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NOISE LEVELS OF COMMON CONSTRUCTION POWER TOOLS By GREGORY CALLAHAN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN BUILDING CONSTRUCTION UNIVERSITY OF FLORIDA 2004 TABLE OF CONTENTS page LIST OF TABLES............................................................................................................. iii LIST OF FIGURES .............................................................................................................v ABSTRACT...................................................................................................................... vii CHAPTER 1 INTRODUCTION......................................................................................................1 Hearing Damage in Construction...............................................................................1 Sources of Sound........................................................................................................1 Aims and Objectives ..................................................................................................2 2 LITERATURE REVIEW...........................................................................................4 Properties of Sound ....................................................................................................4 Effects of Sound from More Than One Source..........................................................6 OSHA Regulations.....................................................................................................8 Hearing Damage.......................................................................................................11 3 RESEARCH METHODOLOGY .............................................................................13 Selection of Tools.....................................................................................................13 Measurements...........................................................................................................14 4 RESULTS.................................................................................................................24 5 CONCLUSION ........................................................................................................45 6 RECOMMENDATIONS .........................................................................................48 LIST OF REFERENCES...................................................................................................51 BIOGRAPHICAL SKETCH .............................................................................................52 ii LIST OF TABLES Table page 2-1 Scale for Combining Decibels....................................................................................7 2-2 Change in decibel levels as a function of the distance from the source.....................7 4-1 Porter Cable Circular Saw Center of Room .............................................................29 4-2 Computed Decibel Levels ........................................................................................29 4-3 Black and Decker Circular Saw Center of Room ....................................................30 4-4 Saws All Center of Room.........................................................................................31 4-5 Router Center of Room ............................................................................................31 4-6 Drill Center of Room................................................................................................32 4-7 Two Circular Saws Center of Room ........................................................................32 4-8 Miscellaneous Tools.................................................................................................33 4-9 Beltsander Center of Room ......................................................................................33 4-10 Porter Cable Circular Saw Corner of Room.............................................................34 4-11 Saws All Corner of Room ........................................................................................35 4-12 Router Corner of Room............................................................................................35 4-13 Drill Corner of Room ...............................................................................................35 4-14 Two Circular Saws Corner of Room........................................................................36 4-15 Beltsander Corner of Room......................................................................................36 4-16 Porter Cable Circular Saw Against Wall Indoors ....................................................37 4-17 Drill Against Wall Indoors.......................................................................................38 4-18 Saws All Against Wall Indoors................................................................................38 iii 4-19 Beltsander Against Wall Indoors .............................................................................38 4-20 Router Against Wall Indoors....................................................................................39 4-21 Two Circular Saws Against Wall Indoors................................................................39 4-22 Porter Cable Circular Saw Open Field Measurement ..............................................40 4-23 Black and Decker Circular Saw Open Field Readings ............................................41 4-24 Two Circular Saws Open Field Readings ................................................................41 4-25 Porter Cable Circular Saw Outdoors Corner............................................................42 4-26 Two Circular Saw Outdoor Corner ..........................................................................42 4-27 Porter Cable Circular Saw Outside Against Wall ....................................................43 4-28 Two Circular Saws Outside Against Wall ...............................................................44 iv LIST OF FIGURES Figure page 2-1 Soundwave .................................................................................................................5 3-1 Sound Level Meter ...................................................................................................13 3-2 Inside Center of Room Decibel Level Measurements .............................................16 3-3 Corner of Room Sound Level Measurements ..........................................................17 3-4 Indoor Against Wall Sound Level Measurement .....................................................18 3-5 Open Field Sound Level Measurements ..................................................................20 3-6 Outdoor Corner Sound Level Measurement ............................................................21 3-7 Outdoor Against Wall Sound Level Measurements.................................................22 4-1 Center of Room Noise Levels ..................................................................................25 4-2 Reading Location Differences..................................................................................26 4-3 Porter Cable Circular Saw Measurements ...............................................................27 4-4 Comparison of Two Circular Saws to One Circular Saw ........................................28 v Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Building Construction NOISE LEVELS OF COMMON CONSTRUCTION POWER TOOLS By Gregory Callahan May, 2004 Chair: Jimmie Hinze Major Department: Building Construction The hearing loss of workers in the construction industry is significant. There has been research performed to measure the noise levels of equipment and tools in the construction industry, but the results of those studies are vague and unclear. The purpose of this study is to measure the noise level of numerous common power tools, with the use of sound level meter, in order to place more definite decibel levels on tools. The tools measured in the study were portable carpenter hand power tools. The tools were selected because the tools are present on almost all jobsites, regardless of the size of the project. These more definite numbers will enable employees in the construction industry to better guard against hearing loss. The goal of the study is to better understand the magnitude of the sound levels of common power tools used in the construction industry. This includes developing an understanding of the nature of sound as impacted by distance. Also the nature of sounds in different environments are explored to discover the different sound levels in numerous situations, to determine which situations place workers at greater risk. The physics of vii sound is researched and compared with the results taken to help clarify the data taken in the study. viii CHAPTER 1 INTRODUCTION Hearing Damage in Construction The loss of hearing by employees within the construction industry is significant. Over an extended period of time exposure to loud sounds that are produced on the construction site can cause hearing damage. It has been a belief within the construction industry, that construction workers, who are employed for long periods of time, over ten years, will have hearing loss. The loss of hearing is an enormous problem that many continue to ignore. “Despite the fact that it is 100 percent preventable, loss of hearing is one of the most prevalent occupational diseases in the United States and the second highest self-reported workplace injury or illness.” 1 Hearing loss of workers can have a drastic negative affect on their lives. Although this problem has been known for a long time there is little knowledge or research about construction noise that would help to understand the sounds that cause this prevalent damage. Sources of Sound A vast number of power tools are utilized on virtually every construction project, from the smallest house to the largest skyscraper being constructed. Despite this, information on the noise levels of common power tools is vague. For instance, OSHA regulations state that 90 decibels are allowed over an eight hour period of time. But, what does that mean, or what produces noise levels of 90 decibels? There is generic information on these types of questions, but no real valuable information. For instance, a 1 http://www.cdc.gov/niosh/pdfs/2001-157.pdf 1 2 circular saw can be said to produce 90 decibels of sound, but what does that mean. Is the circular saw 90 decibels when cutting wood or just running? Is it at a 90 decibel sound level to only the operator of the saw? How are other workers in the room affected by the saw and how close to the saw do they have to be for them to be in danger of hearing damage? Where is the saw being measured, in the center of a room, corner of room, or an open field? Does the location of the source make a difference? These questions demonstrate the complexity of understanding noise. There needs to be a better understanding of the dynamics of sound in construction in order to effectively reduce the alarming rate of hearing loss of workers. This misunderstanding of sound is a reason why there are so few workers that wear hearing protection. Many people in the construction industry know the noise levels allowed by OSHA, less than 90 decibels over an 8 hour period, yet these numbers mean nothing to the workers since they do not know what produces sounds of 90 decibels. Aims and Objectives The hearing loss of workers in the construction industry is significant. There has been research performed to measure the noise levels of equipment and tools in the construction industry, but the results of those studies are vague and unclear. The purpose of this study is to measure the noise level of numerous common power tools, with the use of sound level meter, in order to place more definite decibel levels on tools. The tools measured in the study were portable carpenter hand power tools. The tools were selected because the tools are present on almost all jobsite, regardless of the size of the project. These more definite numbers will enable employees in the construction industry to better guard against hearing loss. The goal of the study is to better understand the magnitude of the sound levels of common power tools used in the construction industry. This includes 3 developing an understanding the nature of sound as impacted by distance. Also the nature of sounds in different environments is explored to discover the different sound levels in numerous situations, to determine which situations place workers at greater risk. The physics of sound is researched and compared with the results taken to help clarify the data taken in the study. CHAPTER 2 LITERATURE REVIEW Properties of Sound Sound is a pressure wave that can be detected by the human ear. The pressure wave is created by a change in pressure in the atmosphere from some type of vibration or turbulence. Noise is unwanted sound. “Two basic characteristics of sound waves important to the subject of noise control are 1. The amplitude, or peak intensity of the wave 2. The frequency in which the pressure peaks occur. Our sense of hearing can detect both of these characteristics. Pressure intensity is sensed as loudness. Whereas pressure is sensed as pitch.” 1The number of cycles that the sound produces in one second is the frequency of the sound. The frequency is measured in hertz, which is calculated with the use of a stroboscope. The range of hertz that a human being can detect is approximately 20 to 20,000 hertz (see figure 2.1). The frequency of a sound is the detected by human beings as the pitch of that sound. In this study the intensity of sound is examined, not the pitch. Intensity of sound, or the strength of the sound, is the wave height that is produced. The strength of the sound is perceived by human ears as the loudness of sound. The intensity of sound, the focus of this study, is measured in decibels. Decibels are measured by the use of sound level meter. The meter measures the sound and expresses the reading in decibels. Decibels are determined by a logarithmic scale, similar to the 1 pg 209, Asfahal, C. Ray, Industrial Safety and Health Management 4 5 Richter scale in the measurement of earthquakes. The equation that determines the change in the decibel level is 20 * log (D1/D2). If d1 is greater than d2, the decibel level will be positive, meaning that the decibel reading is greater at a distance of d2 from the sound source. This means that a sound with an intensity of 90 decibels has ten times more power than a sound that has a reading 80 decibels, and when there is a difference of 20 decibels the power is 100 times as strong. A one decibel change would be undetectable to humans, but a ten decibel difference, although ten times as strong would only be perceived as twice as loud. The need to use the logarithmic scale is because that the loudest sound that a human can hear is ten million times greater than the softest sound detectable to human ears. Therefore to express these readings in more understandable numbers decibels is used. Period ( # of hertz) Wave Height (# of decibels) Time Figure 2-1 Soundwave 6 Effects of Sound from More Than One Source When there is more than one source of sound the decibel level reacts in a certain manner. For instant if two tools that produce the same decibel level individually are operating simultaneously, then the decibel level rises in a manner that one may not think. “If a machine in the plant is very loud, putting a second machine just like it right beside it will not make the sound twice as loud. Remember that the range of sound pressures is tremendous and that the human ear hears only a slight increase in loudness, when the actual sound pressure may have doubled due to the addition of the extra machine. The decibel scale recognizes the addition of the new machine as an increase in noise level of only 3 decibels. Conversely, if the noise level in the plant exceeds allowable standards by very much, shutting off half the machines in the plant – an obviously drastic measure – may have very little effect in bringing down the total noise level on the decibel scale. Table 2.1 provides a scale for combining decibels to arrive at a total noise level from two sources. If there are three or more sources, two sources with the highest decibel levels are combined and then treated as one source to be combined with a third, and so on, until all sources have been combined into a single total.”2 The sound pressure level equation enables one to determine the difference in decibel levels from one distance to another distance. The equation is 20 * Log (Distance 1/ Distance 2). The result of this equation enables one to examine the decrease or increase as one moves away from or towards a noise source. The distances in the measurements in this study were plugged into the sound pressure level equation and the estimated decibel level differences are determined. 2 pg .212, Asfahal, C. Ray, Industrial Safety and Health Management. 7 Table 2-1. Scale for Combining Decibels Difference between two decibel levels to added Amount to be added to larger level to obtain (db) decibel sum (db) 0 3 1 2.6 2 2.1 3 1.8 4 1.4 5 1.2 6 1 7 0.8 8 0.6 9 0.5 10 0.4 11 0.3 12 0.2 Source: NIOSH (ref Industrial Noise) A negative decibel change implies as a drop in the decibel reading from d1 to d2. The exact measurements were not used, but a half a foot either side of the measurement was used, because the measurements might have not been exact. Table 2-2. Change in decibel levels as a function of the distance from the source. d1 1 2 6 20 15 5 d2 2 5 15 8 2 2 0.5 0.4 0.4 2.5 7.5 2.5 -6.02 -7.95 -7.95 7.95 17.50 7.95 d1/d2 decibel drop 8 OSHA Regulations OSHA regulations state the time limits for certain decibel levels of noise exposure, and if the sound levels exceed that level then hearing protection should be provided to the worker. As stated previously these numbers are obtuse and insignificant, because they do not relate useful information to the construction personnel. For example if the regulations stated that if a power circular is being used in an enclosed room all individuals within a 20 foot radius circle should be wearing hearing protection. These type of prescriptive standard would communicate to workers more understandable information, instead of just setting regulations on decibel levels. This is the primary reason why hearing loss is such epidemics within the construction industry, i.e., most of workers do not know exactly what puts them at risk of damaging their hearing. The following are the OSHA provisions of the Code of Federal Regulations (CFR) that pertain to occupational noise exposure and hearing protection. “ CFR 1926.52(a) Protection against the effects of noise exposure shall be provided when the sound levels exceed those shown in Table D-2 of this section when measured on the A-scale of a standard sound level meter at slow response. CFR 1926.52(b) When employees are subjected to sound levels exceeding those listed in Table D-2 of this section, feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels within the levels of the table, personal protective equipment as 9 required in Subpart E, shall be provided and used to reduce sound levels within the levels of the table. CFR 1926.52(c) If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous. CFR 1926.52(d) CFR 1926.52(d)(1) In all cases where the sound levels exceed the values shown herein, a continuing, effective hearing conservation program shall be administered. TABLE D-2 - PERMISSIBLE NOISE EXPOSURES __________________________________________________ | Sound level Duration per day, hours | dBA slow | Response _________________________________________________ | 8.................................| 90 6.................................| 92 4.................................| 95 3.................................| 97 2.................................| 100 1 1/2...........................| 102 1.................................| 105 1/2..............................| 110 1/4 or less.................. | 115 ___________________________________|______________ CFR 1926.52(d)(2) CFR 1926.52(d)(2) CFR 1926.52(d)(2)(i) 10 When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. Exposure to different levels for various periods of time shall be computed according to the formula set forth in paragraph (d)(2)(ii) of this section. CFR 1926.52(d)(2)(ii) F(e)=(T(1)divided by L(1))+(T(2)divided by L(2))+ ... + (T(n) divided by L(n)) where: F(e) = The equivalent noise exposure factor. T = The period of noise exposure at any essentially constant level. L = The duration of the permissible noise exposure at the constant level ( Table D- 2). If the value of F(e) exceeds unity (1) the exposure exceeds permissible levels. CFR 1926.52(d)(2)(iii) A sample computation showing an application of the formula in paragraph (d)(2)(ii) of this section is as follows. An employee is exposed at these levels for these periods: 110 db A 1/4 hour. 100 db A 1/2 hour. 90 db A 1 1/2 hours. F(e) = (1/4 divided by 1/2)+(1/2 divided by 2)+(1 1/2 divided by 8) F(e) = 0.500+0.25+0.188 F(e) = 0.938 Since the value of F(e) does not exceed unity, the exposure is within permissible limits. 11 CFR 1926.52(e) Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.”(OSHA pg 146) CFR 1926.101(a) Wherever it is not feasible to reduce the noise levels or duration of exposures to those specified in Table D-2, Permissible Noise Exposures, in 1926.52, ear protective devices shall be provided and used. CFR 1926.101(b) Ear protective devices inserted in the ear shall be fitted or determined individually by competent persons. CFR 1926.101(c) Plain cotton is not an acceptable protective device.”3 Hearing Damage Workers exposed to noises in the construction industry are at risk of permanent hearing loss. The loss of hearing has an extreme negative affect on the lives of workers. Obviously, the ability to communicate with others becomes difficult. This will put a strain on everyday activities as well as hobbies such as listening to music. It can also put the individual in danger of being injured, because of the inability to hear certain sounds. The loss of hearing also has other health implications such as an increased risk of heart disease, high blood pressure and strokes. 3 http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10625 12 The origin of hearing loss is the exposure to loud noises. Within the human ear are fragile hair cells, and when exposed to loud noise over an extended period of time, the hair cell will become permanently damaged. The small tip of the hair cell, named the cilia, will be either damaged or break off as the level of the sound increases. These hair cell do not have the ability to grow back or heal themselves, therefore if damage is done, it is permanent. Most damage is due to prolonged exposure to loud noises, although damage can be due through a quick intense noise. Exposure to an 85 or greater decibel level over an extended period of time will cause permanent hearing loss.4 4 http://www.cdc.gov/niosh/topics/noise/ CHAPTER 3 RESEARCH METHODOLOGY The measurements in the study performed were done with a sound level meter from Radio Shack. The Sound Level Meter was set on a weighting of A and at slow response for all readings. The following is the information on the sound level meter used in the study from the Radio Shack website (radioshack.com). Figure 3-1 Sound Level Meter “The meter precisely measures area noise and other sound levels. You can then use an equalizer to fine-tune your stereo or home theater system's audio response to match the acoustic environment. The meter's wide-range sound capture reads from 50 to 126dB SPL in seven ranges with slow or fast response for checking peak and average levels.”1 Selection of Tools The tools tested in the study included some of the most common portable power tools that are used on all construction projects. These are the tools selected: 1. Reciprocating Saw (Saws All): Milwaukee 4.0 amps, 120 Volts 1 www.radioshack.com 13 14 2. Router: Black and Decker Deluxe Router 7615 3. Belt Sander: Sears Craftsman Belt Sander Model 315-11721, 120 Volts, 7.0 Amps 4. Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm 5. Circular Saw: Black & Decker 7390 7.25 inch blade 6. Drill: Black & Decker, CD 1200, 12 Volt 7. Jig Saw 4935, 120 volts, 3.2 Amps 8. Electric Planer: Hitachi F-20A, 3.4 Amps 9. 9” Sander/Grinder Sears Craftsman 2 HP 10. Ryobi: Detail Carver DC 500 Measurements The choices of measurements of the sound levels of the different wood working tools were picked to simulate the different situations in which the tools might be used. The tools were set in both outside situations and inside situations. All readings are taken with the tools turned on and not applied to wood, and turned on and applied to wood. Readings were taken at various distances for each situation, three measurements taken for each location three times, the three measurements were recorded, and the average reading was computed and recorded. Inside Measurements The measurements were taken in one room with dimensions of 40 feet long by 30 feet wide. The walls of the room were constructed with concrete masonry units. The floor of the room is made with steel troweled concrete. The ceiling is made of a dropped 10 foot acoustical ceiling. All of the tools were tested in these following situations: 15 In the middle of the room. End tool was placed directly in the middle of the room, 15 feet from the side walls and 20 feet from the end walls. The tool was set on the top of a table 30 inches off the floor. In all instances, when measurements were taken, three separate readings were taken per location. Readings were first taken at 6 inches from the tool. Readings were then taken 24 inches above the tool, to simulate the decibel level that the operator of the tool would experience. Then readings were taken at 6 feet behind, in front, to the left and to the right, of the tool. These readings were taken to determine the amount of sound level variation at the six foot radius about the tool. Variations were assumed to be attributed to the room configuration and to the position of the tool user. The next readings were taken at 15 feet in front (orientation based on the tool user position) and behind the tool and 13 feet to the left and right of the tool. The measurements on the side were 13 feet because of the restriction of the room, the individual holding the sound level meter stood with that individual’s back to the wall, so the meter was approximately 13 feet from the center of the room. The sound levels of ten different tools were measured in this setting (see Figure 3.2). In the corner of the room. In another series of measurements, the tool being tested was placed directly in the corner of the room 16 inches from the two adjoining walls. The operator of the tool faced the corner. The tool was set on top of the table 30 inches off the floor. As before, readings were taken at 6 inches from the tool and 24 inches above the tool. Then readings were taken at 6 feet behind the tool ( based on the operator position), and to the left and to the right of the tool. The next readings were 16 G C 13’ 6’ H Tool D F J 30’ 6’ E 13’ Operator I 6’ 15’ A= location of sound reading 6” from tool. B= sound reading taken at 24” above tool (ear level of operator) 40’ Figure 3-2 Inside Center of Room Decibel Level Measurements Tools Measured: 1. Reciprocating Saw (Saws All): Milwaukee 4.0 amps, 120 Volts 2. Router: Black and Decker Deluxe Router 7615 3. Belt Sander: Sears Craftsman Belt Sander Model 315-11721, 120 Volts, 7.0 Amps 4. Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm 5. Circular Saw: Black & Decker 7390 7.25 inch blade 6. Drill: Black & Decker, CD 1200, 12 Volt 7. Jig Saw 4935, 120 volts, 3.2 Amps 8. Electric Planer: Hitachi F-20A, 3.4 Amps 9. 9” Sander/Grinder Sears Craftsman 2 HP 10. Ryobi: Detail Carver DC 500 taken at 30 feet from the tool directly behind the operator and 15 feet to the left and right of the tool, along the wall. The sound levels of six different tools were measured in this setting (see Figure 3.3). 17 Against the wall. A third series of readings were taken with the tool placed directly in the middle of the 30 foot wall 16 inches from the wall. The operator of the tool faced the wall. The tool was set on the top of a table 30 inches off the floor. Readings were taken at 6 inches from the tool and 24 inches above the tool. Then a series of readings were taken 6 feet from the tool, one behind the operator, one to the left and one to the right of the operator. The next readings were taken at a distance of 15 feet directly behind the operator and 13 feet to the left and right of the operator of the tool. The sound levels of six different tools were measured in this setting (see Figure 3.4). 15’ 6’ F A= location of sound reading 6” from tool. B= sound reading taken at 24” above tool (ear level of operator) Tool 16” from corner C 6’ D (6’ from tool) E H G Operator (30’ from tool) 40’ Figure 3-3 Corner of Room Sound Level Measurements 15’ 30’ 18 Tools Measured: 1. Reciprocating Saw (Saws All): Milwaukee 4.0 amps, 120 Volts 2. Router: Black and Decker Deluxe Router 7615 3. Belt Sander: Sears Craftsman Belt Sander Model 315-11721, 120 Volts, 7.0 Amps 4. Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm 5. Circular Saw: Black & Decker 7390 7.25 inch blade 6. Drill: Black & Decker, CD 1200, 12 Volt F Operator C 13’ 6’ D G 30’ (6’ from tool) (30’ from tool) 6’ E 13’ H Tool 40’ A= location of sound reading 6” from tool. B= sound reading taken at 24” above tool (ear level of operator) Figure 3-4 Indoor Against Wall Sound Level Measurement Tools Measured: 1. Reciprocating Saw (Saws All): Milwaukee 4.0 amps, 120 Volts 2. Router: Black and Decker Deluxe Router 7615 3. Belt Sander: Sears Craftsman Belt Sander Model 315-11721, 120 Volts, 7.0 Amps 4. Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm 5. Circular Saw: Black & Decker 7390 7.25 inch blade 6. Drill: Black & Decker, CD 1200, 12 Volt 19 Outdoor Measurements Measurements were taken outdoors to compare the sound measurements with the indoor conditions of the 30’ by 40’ room. Therefore the measurements taken outside were otherwise intended to be similar to the indoor measurement situations. Measurements in the open outdoors. The tool was tested 91 feet from the nearest building, with the operator of the tool facing away from the building. The measurements taken were similar to the readings taken for the middle of the room conditions. The tool was set on the top of a table 30 inches off the ground, which was grass and dirt. Readings are taken at 6 inches from the tool and 24 inches above the tool. Then readings are then taken 6 feet from the tool: behind, in front, to the left and to the right of the operator. Readings were then taken at 15 feet from the tool in front of the operator, behind the operator, and 15 feet to the left and right of the operator. Three tools were measured in this condition, namely the two circular saws: Porter Cable 7.25 inch blade model 347, and the Black & Decker 7390 7.25 inch blade. Measurements were also taken with both circular saws simulataneousley operating (see Figure 3.5). 20 G A= location of sound reading 6” from tool. B= sound reading taken at 24” above tool (ear level of operator) C 15’ 6’ H Tool D F J 6’ Nearest Building 81’ feet from Building E Operator 15’ I 6’ 15’ 6’ 15’ Figure 3-5 Open Field Sound Level Measurements In corner outdoors. Similar to the testing done inside the room the tool was tested in an outdoors corner. The tools being measured were placed in a 90 degree corner of a 8 foot high brick wall. The walking surface was rough finished concrete. The tool being tested was placed directly in the corner of the wall 16 inches from the two adjoining walls. The operator of the tool faced the corner. The tool was set on the top of a table 30 inches off the ground. Readings are taken at 6 inches from the tool and 24 inches above the tool. Then readings were taken at 6 feet from the tool: behind, to the left and to the right of the operator. The next readings were taken at 15 feet from the tool: behind the operator and 15 feet to the left and to the right of the operator. Two tools were measured in this setting, a circular saw: Porter Cable 7.25 inch blade model 347, and two circular saws simulataneousley operating (see Figure 3.6). 21 Building Tool F A= location of sound reading 6” from tool. B= sound reading taken at 24” above tool (ear level of operator) C 6’ D E Operator 15’ G (15’ from tool) H 8’ High Brick Wall 15’ 6’ Figure 3-6 Outdoor Corner Sound Level Measurement Against the wall outdoors. Sound measurements were taken against a 38 foot outdoor wall. The wall was constructed of insulated metal panels. Sound measurements taken were similar to the readings taken against the wall inside the room, for the purpose of making comparisons. The operator of the tool faced the wall. The tool was set on the top of a table 30 inches off the rough finished concrete ground. Readings were taken at 6 inches from the tool and 24 inches above the tool. Then readings are taken at 6 feet from the tool behind, to the left and to the right, of the operator. The next readings were taken at 15 feet from the tool behind the operator and 15 feet to the left and right of the operator. In this setting two tools were measured for sound levels produced, a circular saw: Porter Cable 7.25 inch blade model 347, and two circular saws simulataneousley operating (see Figure 3.7). 22 A = lo c a tio n o f s o u n d r e a d in g 6 ” fro m to o l. B = s o u n d r e a d in g ta k e n a t 2 4 ” a b o v e to o l (e a r le v e l o f o p e ra to r) Tool H 15’ E 6’ G D (6 ’ fro m to o l) 6’ (3 0 ’ fro m to o l) C 15’ O p e ra to r F B u ild in g Figure 3-7 Outdoor Against Wall Sound Level Measurements Two Tool Measurements Measurements taken with two tools turned on at the same time. Because of safety concerns, no measurements were taken with two tools cutting wood at the same time; all measurements were taken with the tools freewheeling. The two tools used in the two tool readings were the Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm, and the Circular Saw: Black & Decker 7390 7.25 inch blade. There was one operator for both tools. The operator had one saw in each hand in the prescribed positions as described previously. All the situations described earlier (indoor and 23 outdoor) were repeated for the two tool readings. The tools were measured for sound levels in all settings previously described. CHAPTER 4 RESULTS The results are calculated by measuring the sound level three times for each measurement. The average of the three readings was then calculated and recorded in tables. For each measurement location a letter was assigned. The letters in the table depict the placement of the sound level meter in relation to the tool, and correspond to the sound measurement location shown in Figures 3.2 to 3.7. When a letter in the tables is followed by an apostrophe (’) this indicate that this measurement was taken while the tool was cutting wood. No mark next to the letter means that the tool was measured while not cutting wood. Center of room noise levels. Five tools were evaluated in the center of the room condition. To illustrate the drop in decibels with the distance from the tool, a simple figure was created. Figure 4.1 shows the sound level measurements at location A (6 inches from the tool), B (24 inches above the tool), F (6 feet in front of the tool), G (15 feet in front of the tool). All measurements shown in Figure 4.1 were taken while the tools were not cutting wood. (refer back to Figure 3.2). In addition, an arbitrary value of 95 decibels was assigned as a fictional sound level reading at position A. Computations were made to determine the decline in decibels as a function of the distance from the tool. The computations show that the sound level would decline 29.7 decibels from the location of the tool to a position of 15 feet from the tool (computed value is the dark line in Figure 4.1) 24 25 Sound Measurements of the six tools declined with distance from the tool, but the decline was not as extreme as the computed number. The decibel drop for the tools that were measured ranged from 17.3 to 18.3 decibels. Thus, it is apparent that the sound level decline, which was consistent among the tools, was considerably less than would be predicted by the formula alone. Sound measurements were taken with the additional four tools but only at the 6 inch and 24 inch locations. 110 100 Assigned value Decibel 90 Computed PC circular saw Saws All Router Drill Beltsander BD circular saw 80 70 60 50 A =.5 ft. B=2 ft C=6 ft G=15 ft Distance Figure 4-1 Center of Room Noise Levels Body position. The results clearly show that the position of the operator significantly affect the decibel level of sound emitted by tools. The data from the tables consistently demonstrate that readings taken somewhat behind the tool operator (positions D, E, H, and I) had lower sound levels than the other measurements. As shown 26 in Figure 3.2 to 3.7 the body of the operator is in the path of the sound in the measurements D, E, H, and I. This characteristic can also be seen from Figure 4.2. This graph demonstrates the results of the six feet measurements of the Porter Cable Circular Saw in all settings, while cutting wood. Clearly the 6’ back and the 6’ left measurements are lower than the other measurements, with few exceptions. 110 108 106 104 102 100 Decibel 98 96 6' front 6' back 6' Left 6' right 94 92 90 88 86 84 82 80 78 Center of Room Indoor against Wall Indoor Corner Open Area Outdoor Outdoor Against Outdoor Corner wall Measurement Situation Figure 4-2 Reading Location Differences Porter cable circular saw in all measurement settings. In Figure 4.3 the Porter Cable circular Saw is shown in all settings, measured at 24 inches from the tool, while cutting wood and not cutting wood. The graph shows how one tool had drastically different sound levels, depending on the environment in which it was measured and depending whether or not it was cutting wood. The tool had the highest sound levels in the corner of the room. This high reading is because of the reflection of sound from the 27 walls. The lack of reflection of sound was the reason the lowest reading was from the outdoor open area reading. This demonstrates that the environment that a tool is measured will affect the sound level drastically. 110 105 Decibel 100 Not Cutting at 24" Cutting 24" 95 90 85 Center of Room Indoor Against Indoor against Wall Corner Open Area Outdoor Outdoor Against wall Outdoor Corner Reading Situation Figure 4-3 Porter Cable Circular Saw Measurements Comparison of two circular saws to one circular saw in all measurement situations. Figure 4.4 displays the sound levels of two circular simultaneously running without cutting wood, the sound level of one circular saw running without cutting wood, and the computed sound levels of the two saws determined from Table 2.1. The sound levels shown are for all situations with the sound level meter at 24 inches from the tool. The graph shows that the computed value for the sound level of two tools is not accurate in comparison to the actual readings taken. Again this demonstrates that the computed values of sound levels are not accurate, because of the various environments in which the sound levels can be measured. 28 103 101 99 Decibel 97 Porter Cable Saw at 24" 2 Circular Saws 95 Computed 93 91 89 87 Center of Room Indoor against Wall Indoor Corner Open Area Outdoor Outdoor Against wall Outdoor Corner Measurement Situation Figure 4-4 Comparison of Two Circular Saws to One Circular Saw Center of room results. The Porter Cable circular saw sound level results for the middle of the room were recorded in Table 4.1. The various measurement locations were shown on the left hand column. The locations of the measurements as are illustrated in Figure 3.2. Three different readings were taken for each measurement location and are shown in Table 4.1 as Reading 1, Reading 2 and Reading 3. The average of these readings was calculated and recorded under the Average column heading. In the far right hand column is the computed decibel value. The A and A’ in the computed column were assigned values, therefore the average of the actual readings in those locations was used. The remaining computed values were calculated by using the sound pressure level equation, 20 * Log (Distance 1/ Distance 2). Table 4.2 illustrates the calculated decibel drop using the sound pressure level equation. The calculated values were subtracted from 29 both the A and A’ values, to determine the predicted sound level at different distances. These calculations were recorded in the computed column of Table 4.1, and are shown to illustrate the differences in the actual sound level readings and the computed sound levels. Table 4-1. Porter Cable Circular Saw Center of Room Circular Saw: Center of Room Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' Reading 1 100 115 92 108 90 96 85 94 81 95 88 98 84 91 80 95 81 95 83 92 Reading 2 101 115 93 109 89 95 84 95 81 96 89 98 83 92 80 94 81 95 84 92 Reading 3 102 114 93 108 90 95 85 96 81 97 88 98 84 91 81 95 81 95 84 92 Average 101.0 114.7 92.7 108.3 89.7 95.3 84.7 95.0 81.0 96.0 88.3 98.0 83.7 91.3 80.3 94.7 81.0 95.0 83.7 92.0 Computed 101 114.7 88.96 102.66 79.42 93.12 79.42 93.12 79.42 93.12 79.42 93.12 71.5 85.2 71.5 85.2 71.5 85.2 71.5 85.2 Table 4-2. Computed Decibel Levels Computed No Range d1 d2 d1/d2 decibel drop 0.5 2 0.25 -12.0412 0.5 6 0.083333 21.58362 0.5 15 0.0333333 -29.54243 Tables 4.3 to Table 4.9 represent the remaining tools that were measured for sound levels in the center of the room. The tables were recorded in the same manner as Table 4.1, except that the computed decibel value was not calculated in Tables 4.3 to 4.9. The tools in order of the tables are. 30 Table 4.3 Circular Saw: Black & Decker 7390 7.25 inch blade Table 4.4 Reciprocating Saw (Saws All): Milwaukee 4.0 amps, 120 Volts Table 4.5 Router: Black and Decker Deluxe Router 7615 Table 4.6. Drill: Black & Decker, CD 1200, 12 Volt Table 4.7 Two Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm and Circular Saw: Black & Decker 7390 7.25 inch blade Table 4.8 Miscelleneous Tools: Jig Saw 4935, 120 volts, 3.2 Amps, Electric Planer: Hitachi F-20A, 3.4 Amps 9” Sander/Grinder Sears Craftsman 2 HP Ryobi: Detail Carver DC 500 Table 4.9 Belt Sander: Sears Craftsman Belt Sander Model 315-11721, 120 Volts, 7.0 Amps. Table 4-3. Black and Decker Circular Saw Center of Room Circular Saw: Center of Room Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' Reading 1 101 115 92 109 91 97 85 95 82 96 90 99 84 92 81 97 82 95 85 93 Reading 2 102 116 94 109 90 95 86 97 80 96 91 98 85 93 81 96 82 96 84 93 Reading 3 102 114 94 108 90 96 86 96 83 98 92 99 83 91 81 95 81 95 85 92 Average 101.7 115.0 93.3 108.7 90.3 96.0 85.7 96.0 81.7 96.7 91.0 98.7 84.0 92.0 81.0 96.0 81.7 95.3 84.7 92.7 31 Table 4-4. Saws All Center of Room Saws All: Center of Room Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' Reading 1 98 101 89 92 85 87 85 81 86 86 85 88 80 78 78 76 78 80 79 82 Reading 2 98 101 88 91 84 88 86 81 85 86 85 89 79 79 79 77 79 79 80 82 Reading 3 98 101 89 91 86 87 85 82 85 87 85 88 80 79 78 76 78 79 80 82 Table 4-5. Router Center of Room Router: Center of Room Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' Reading 1 102 102 99 100 89 100 91 93 88 90 90 94 84 87 84 87 85 87 88 88 Reading 2 103 101 98 101 89 101 92 94 88 91 91 95 85 88 84 88 86 87 89 89 Reading 3 103 101 99 101 90 101 92 93 88 90 90 95 85 88 84 88 85 87 88 89 Average 102.7 101.3 98.7 100.7 89.3 100.7 91.7 93.3 88.0 90.3 90.3 94.7 84.7 87.7 84.0 87.7 85.3 87.0 88.3 88.7 Average 98.0 101.0 88.7 91.3 85.0 87.3 85.3 81.3 85.3 86.3 85.0 88.3 79.7 78.7 78.3 76.3 78.3 79.3 79.7 82.0 32 Table 4-6. Drill Center of Room Drill: Center of Room Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' Reading 1 76 83 71 79 64 70 66 70 64 68 68 71 60 63 59 62 60 60 59 61 Reading 2 77 83 72 78 65 71 66 71 64 68 68 71 59 62 60 61 59 61 59 61 Reading 3 77 83 72 79 64 70 66 72 64 69 69 71 59 63 59 62 59 61 60 61 Average 76.7 83.0 71.7 78.7 64.3 70.3 66.0 71.0 64.0 68.3 68.3 71.0 59.3 62.7 59.3 61.7 59.3 60.7 59.3 61.0 Table 4-7. Two Circular Saws Center of Room Both Circular Saws Center of Room Location A B C D E F G H J Reading 1 110 96 92 88 99 88 84 90 89 Reading 2 111 97 93 89 99 89 85 91 90 Reading 3 109 96 91 88 97 89 86 92 89 In Table 4.8 only the 6 inch and the 24 inch sound level readings were recorded. Only these readings were used because these tools are not as common on construction jobsites as the other tools recorded. Indoor corner of room readings. The results of the sound level readings from the tools operated in the corner of the 30 feet by the 40 feet room are recorded in Tables Average 110.0 96.3 92.0 88.3 98.3 88.7 85.0 91.0 89.3 33 4.10 to 4.15. The different measurement locations are displayed in the left hand column. The locations of the measurements are as were described in Figure 3.3. Three various Table 4-8. Miscellaneous Tools Miscellaneous Tools Jigsaw Location A Jigsaw Location B Planer Location A Planer Location B Grinder Location A Grinder Location B Carver Location A Carver Location B Reading 1 111 99 118 96 118 108 82 72 Reading 2 112 100 118 96 118 107 84 72 Reading 3 113 99 117 99 121 107 89 77 Average 112.0 99.3 117.7 97.0 119.0 107.3 85.0 73.7 Table 4-9. Beltsander Center of Room Beltsander: Center of Room Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' Reading 1 108 111 103 97 93 94 93 94 95 92 97 92 88 85 88 85 91 88 91 90 Reading 2 109 111 102 97 93 93 94 95 96 93 98 92 87 86 88 84 91 88 91 89 Reading 3 108 112 104 98 93 92 93 95 96 92 97 93 88 86 88 86 92 89 90 90 Average 108.3 111.3 103.0 97.3 93.0 93.0 93.3 94.7 95.7 92.3 97.3 92.3 87.7 85.7 88.0 85.0 91.3 88.3 90.7 89.7 readings are taken for each measurement location and are shown as Reading 1, Reading 2 and Reading 3. The average of these readings was calculated and recorded under the Average column heading on the right side of the tables. The tools measured are listed in order in the following tables; 34 Table 4.10 Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm Table 4.11 Reciprocating Saw (Saws All): Milwaukee 4.0 amps, 120 Volts Table 4.12 Router: Black and Decker Deluxe Router 7615 Table 4.13 Drill: Black & Decker, CD 1200, 12 Volt Table 4.14 Two Circular Saws. Black & Decker 7390 7.25 inch blade, and the Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm Table 4.15. Belt Sander: Sears Craftsman Belt Sander Model 315-11721, 120 Volts, 7.0 Amps. Table 4-10. Porter Cable Circular Saw Corner of Room Circular Saw Corner of Room Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 103 113 99 109 92 101 88 103 91 98 80 93 79 89 81 89 Reading 2 103 114 99 108 92 100 88 104 90 99 80 93 79 88 81 90 Reading 3 104 114 100 109 91 101 87 103 91 98 80 92 80 89 81 90 Average 103.3 113.7 99.3 108.7 91.7 100.7 87.7 103.3 90.7 98.3 80.0 92.7 79.3 88.7 81.0 89.7 Indoor Against Wall Sound Level Measurements. The results of the sound level readings from the tools placed indoors against a 30 foot wall were recorded in Tables 4.16 to 4.21. The different measurement locations were displayed under the column furthest to left in each table. The locations of the measurements are as described 35 Table 4-11. Saws All Corner of Room Saws All: Corner of Room Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 94 92 88 87 79 81 77 79 80 80 75 75 69 70 71 72 Reading 2 93 93 89 87 80 81 77 80 80 81 76 74 69 71 71 71 Reading 3 96 93 88 88 79 80 78 80 80 81 76 74 70 70 71 72 Average 94.3 92.7 88.3 87.3 79.3 80.7 77.3 79.7 80.0 80.7 75.7 74.3 69.3 70.3 71.0 71.7 Table 4-12. Router Corner of Room Router: Corner of Room Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 101 102 92 94 88 90 84 88 84 91 80 77 74 75 75 77 Reading 2 102 102 93 95 88 92 85 88 84 91 84 78 75 74 75 78 Reading 3 100 100 94 94 89 90 85 88 84 92 80 78 75 75 74 77 Average 101.0 101.3 93.0 94.3 88.3 90.7 84.7 88.0 84.0 91.3 81.3 77.7 74.7 74.7 74.7 77.3 Table 4-13. Drill Corner of Room Drill: Corner of Room Location A A' B B' C C' Reading 1 73 75 66 70 62 62 Reading 2 73 75 66 72 62 63 Reading 3 72 76 65 71 63 64 Average 72.7 75.3 65.7 71.0 62.3 63.0 36 Table 4-13 Continued Drill: Corner of Room D D' E E' F F' G G' H H' Reading 1 60 61 61 61 50 54 54 54 60 53 Reading 2 59 62 62 60 52 55 55 55 59 53 Reading 3 60 60 60 62 50 54 54 54 60 53 Average 59.7 61.0 61.0 61.0 50.7 54.3 54.3 54.3 59.7 53.0 Table 4-14. Two Circular Saws Corner of Room 2 Circular Saws Corner Room Location A B C D E F G H Reading 1 109 100 97 99 95 88 87 87 Reading 2 110 101 98 100 96 88 88 88 Reading 3 108 100 99 98 95 88 87 87 Average 109.0 100.3 98.0 99.0 95.3 88.0 87.3 87.3 Table 4-15. Beltsander Corner of Room Beltsander: Corner of Room Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 109 101 98 89 89 84 85 83 88 85 79 79 78 74 78 77 Reading 2 110 101 99 90 89 84 85 84 88 85 78 78 77 75 78 77 Reading 3 108 102 99 89 90 85 86 84 89 86 79 79 77 74 79 78 Average 109.0 101.3 98.7 89.3 89.3 84.3 85.3 83.7 88.3 85.3 78.7 78.7 77.3 74.3 78.3 77.3 37 in Figure 3.4. Three separate readings were taken for each measurement location and are shown as Reading 1, Reading 2 and Reading 3. The average of these readings were calculated and recorded under the average column heading on the far right side of the tables. The following tools are listed in the tables; Table 4.16 Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm Table 4.17 Black & Decker, CD 1200, 12 Volt Table 4.18 Reciprocating Saw (Saws All): Milwaukee 4.0 amps, 120 Volts Table 4.19. Belt Sander: Sears Craftsman Belt Sander Model 315-11721, 120 Volts, 7.0 Amps. Table 4.20 Router: Black and Decker Deluxe Router 7615 Table 4.21 Two Circular Saws. Black & Decker 7390 7.25 inch blade, and the Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm Table 4-16. Porter Cable Circular Saw Against Wall Indoors Circular Saw: Middle of Wall Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 101 113 95 107 89 91 97 96 91 100 83 93 79 89 81 95 Reading 2 101 114 94 108 90 91 97 95 91 100 82 92 80 90 82 94 Reading 3 101 115 95 108 89 92 98 96 92 100 83 93 79 89 81 95 Average 101.0 114.0 94.7 107.7 89.3 91.3 97.3 95.7 91.3 100.0 82.7 92.7 79.3 89.3 81.3 94.7 38 Table 4-17. Drill Against Wall Indoors Drill: Middle of Wall Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 80 84 72 76 62 70 58 68 65 70 56 64 56 57 59 68 Reading 2 79 84 73 77 61 70 58 67 65 69 56 64 55 57 60 66 Reading 3 80 85 72 76 62 69 59 68 65 71 56 64 56 58 59 66 Average 79.7 84.3 72.3 76.3 61.7 69.7 58.3 67.7 65.0 70.0 56.0 64.0 55.7 57.3 59.3 66.7 Table 4-18. Saws All Against Wall Indoors Saws All: Middle of Wall Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 98 93 90 89 79 83 82 83 84 85 74 80 73 75 81 83 Reading 2 98 94 90 90 79 82 83 83 84 86 74 80 74 76 81 84 Reading 3 99 94 89 90 79 82 83 83 84 85 75 81 73 75 80 83 Average 98.3 93.7 89.7 89.7 79.0 82.3 82.7 83.0 84.0 85.3 74.3 80.3 73.3 75.3 80.7 83.3 Table 4-19. Beltsander Against Wall Indoors Beltsander: Middle of Wall Location A A' B B' C C' D D' Reading 1 115 109 102 103 93 91 92 95 Reading 2 114 110 103 103 93 91 92 95 Reading 3 115 110 103 104 94 92 92 94 Average 114.7 109.7 102.7 103.3 93.3 91.3 92.0 94.7 39 Table 4-19 Continued Beltsander: Middle of Wall E E' F F' G G' H H' Reading 1 97 95 87 87 85 85 93 92 Reading 2 98 95 87 88 86 85 94 92 Reading 3 99 95 88 87 85 86 93 92 Average 98.0 95.0 87.3 87.3 85.3 85.3 93.3 92.0 Reading 2 104 106 99 102 88 93 92 93 93 90 81 86 78 83 89 88 Reading 3 105 105 99 101 88 93 93 93 92 91 81 87 79 84 90 88 Average 104.3 105.7 98.7 101.7 88.3 93.3 92.3 92.7 92.7 90.3 81.3 86.3 78.3 83.3 89.3 87.7 Table 4-20. Router Against Wall Indoors Router: Middle of Wall Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 104 106 98 102 89 94 92 92 93 90 82 86 78 83 89 87 Table 4-21. Two Circular Saws Against Wall Indoors 2 Circular Saws Middle of Wall Inside Location A B C D E F G H Reading 1 110 98 94 90 98 87 88 90 Reading 2 112 98 95 91 97 89 89 89 Reading 3 112 99 96 90 99 88 90 89 Average 111.3 98.3 95.0 90.3 98.0 88.0 89.0 89.3 Open field sound level measurements. The results of the sound level measurements in an open field are displayed in Tables 4.22 to 4.24. The measurement 40 locations are shown on the far left column of the table. All the measurement locations are in accordance with the measurement locations noted in Figure 3.5. Three separate readings are taken for each measurement location and are shown as Reading 1, Reading 2 and Reading 3. The average of the three readings taken at each location were calculated and recorded under the average column heading of the tables. The decibels of these readings are substantially lower than the decibel levels of the indoor readings, as was displayed in Figure 4.3. The tables and the tools are shown in the following order; Table 4.22 Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm Table 4.23 Circular Saw: Black & Decker 7390 7.25 inch blade Table 4.21 Two Circular Saws. Black & Decker 7390 7.25 inch blade, and the Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm. Table 4-22. Porter Cable Circular Saw Open Field Measurement Circular Saw: Outside Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' Reading 1 99 112 88 100 82 87 73 91 79 92 80 90 73 81 68 80 72 90 72 81 Reading 2 98 113 88 99 82 88 74 92 80 93 81 90 73 82 67 81 72 89 72 82 Reading 3 100 112 89 100 81 88 73 91 80 93 81 89 72 82 67 80 73 89 73 82 Average 99.0 112.3 88.3 99.7 81.7 87.7 73.3 91.3 79.7 92.7 80.7 89.7 72.7 81.7 67.3 80.3 72.3 89.3 72.3 81.7 41 Table 4-23. Black and Decker Circular Saw Open Field Readings B&D Circular Saw : Outside Reading 1 Reading 2 Reading 3 Location A A' B B' C C' D D' E E' F F' G G' H H' I I' J J' 100 110 87 102 84 91 77 82 87 95 88 90 75 83 67 81 74 93 75 83 101 109 86 103 84 92 77 83 87 95 89 91 76 84 66 82 74 94 75 83 Average 101 110 87 102 83 91 76 83 86 96 88 90 77 83 67 81 75 94 74 84 100.7 109.7 86.7 102.3 83.7 91.3 76.7 82.7 86.7 95.3 88.3 90.3 76.0 83.3 66.7 81.3 74.3 93.7 74.7 83.3 Table 4-24. Two Circular Saws Open Field Readings 2 Circular Saws : Outside Location A B C D E F G H I J Reading 1 98 88 82 81 88 87 77 76 77 77 Reading 2 99 88 83 80 88 87 77 76 77 77 Reading 3 99 89 82 81 89 88 76 75 78 76 Average 98.7 88.3 82.3 80.7 88.3 87.3 76.7 75.7 77.3 76.7 Outdoor corner sound level measurements. The results of the sound level measurements in an outdoor corner are shown in Tables 4.25 and 4.26. The measurement locations are visible on the far left column of the table and correspond with the measurement locations shown in Figure 3.6. The average of these readings were calculated and recorded under the Average column heading of the tables. The decibels of these readings are substantially higher than the decibel levels of the other outdoor 42 measurements, similar to the indoor corner measurements. The configuration of a corner results in a lower reduction of the decibel level of a sound, which was displayed in Figure 4.3. The Tables and the tools that the tables represent are in the following order Table 4.25 Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm Table 4.26 Two Circular Saws. Black & Decker 7390 7.25 inch blade, and the Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm. Table 4-25. Porter Cable Circular Saw Outdoors Corner PC Circular Saw Corner Outdoors Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 102 126 98 108 91 104 87 103 91 108 84 96 82 99 81 97 Reading 2 103 125 99 109 92 104 88 104 90 109 84 96 81 98 82 98 Reading 3 102 123 98 110 92 103 87 103 91 107 85 97 82 98 82 98 Table 4-26. Two Circular Saw Outdoor Corner 2 Circular Saws Corner Outside Location A B C D E F G H Reading 1 109 103 99 93 99 89 88 87 Reading 2 110 102 99 94 100 89 87 88 Reading 3 109 103 98 94 99 89 87 87 Average 109.3 102.7 98.7 93.7 99.3 89.0 87.3 87.3 Average 102.3 124.7 98.3 109.0 91.7 103.7 87.3 103.3 90.7 108.0 84.3 96.3 81.7 98.3 81.7 97.7 43 Outside against wall sound level measurements. The results of the sound level measurements of the tools tested on a wall outdoors are displayed in Tables 4.27 and 4.28. The measurement locations are shown in on the left column of the table. All the measurement locations correspond with the measurement locations shown in Figure 3.7. The average of these readings were calculated and recorded under the average column heading of the tables. The tools represented in the tables are shown in the following order; Table 4.27 Circular Saw: Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm Table 4.28 Two Circular Saws. Black & Decker 7390 7.25 inch blade, and the Porter Cable 7.25 inch blade, model 347, 120 volt, 15 Amps, 5800 rpm. Table 4-27. Porter Cable Circular Saw Outside Against Wall Circular Saw: Middle of Wall Outside Location A A' B B' C C' D D' E E' F F' G G' H H' Reading 1 101 119 89 106 74 98 74 97 82 108 75 90 69 94 75 98 Reading 2 102 120 89 107 75 98 75 97 81 108 75 89 68 93 75 99 Reading 3 100 119 88 107 74 97 74 98 81 109 75 90 69 93 76 99 Average 101.0 119.3 88.7 106.7 74.3 97.7 74.3 97.3 81.3 108.3 75.0 89.7 68.7 93.3 75.3 98.7 44 Table 4-28. Two Circular Saws Outside Against Wall 2 Saws: Middle of Wall Outside Location A B C D E F G H Reading 1 109 100 94 88 94 87 81 88 Reading 2 110 101 94 88 96 87 80 88 Reading 3 110 101 95 89 95 86 81 87 Average 109.7 100.7 94.3 88.3 95.0 86.7 80.7 87.7 CHAPTER 5 CONCLUSION The sound level measurements taken in this study are not consistent with the theoretical levels that were determined through the sound pressure level equation 20 * log (D1/D2). When the actual measured data are compared to the theoretical data, the numbers are extremely fairly close, in all measurements both indoors and outdoors. This is extremely important, because it verifies the fact that the equation is not a reliable reference to measure the decibel levels in a work area. The sound level equation is a function of distance. The environment in which sounds are created is not taken into account when the formula is calculated. The results from Figure 4.3 clearly illustrate that the environment in which a sound is produced has a drastic effect on the decibel level. This is clearly illustrated in Figure 4.3. The chart displays the Porter Cable circular saw in all environmental settings. The displayed readings are the 24 inch readings while cutting wood and not cutting wood. If the environment was not a factor of the sound levels then the sound levels for the settings should be the same, but that is not the case. The indoor corner reading has the highest decibel level, 109 decibels. This is because when tool is operated in a corner the sound is reflected. The material of the room also helped to magnify the reflection of sound. The walls were constructed out of concrete masonry units and the floor was concrete. The open field results in were the lowest sound level in Figure 4.3 by a large amount. The ground in this setting was grass, and there were no buildings near to reflect the sound. 45 46 The decibel difference from the saw cutting wood in a corner to the saw not cutting wood in an outdoor open area is 21 decibels. This means that the same tool in one setting produces a sound over 100 times as powerful as the same tool in another setting. The OSHA standards would also be easily violated in one setting and within the OSHA rules in another setting. This obviously demonstrates that when a tool is given a decibel value, such as a circular saw is 90 decibels, the decibel value is not reliable. Figure 4.3 clearly illustrates that the sound pressure level equation can not accurately predict the sound levels of tools because of environmental factors. The numbers from Figure 4.1 also show that the computed sound levels do not take into account the environment where the sounds are produced. The computed value had a 29.7 decibel drop from 6 inches to 15 feet, and the measured tools had a decibel drop between 17.3 decibels to 18.3 decibels. Clearly the materials of the room, the concrete floors and the concrete masonry unit walls, reflected the sound creating a lower decibel drop over a distance than anticipated. This is important, because the sound pressure level equation obviously can not be used to accurately estimate the sound levels in an area. The difference in the computed values to the actual readings was over ten decibels, which as explained earlier, is a significant amount. When comparing the indoor decibel readings to the outdoor decibel readings the initial reading for the outdoor measurements are slightly lower than the indoor measurements, but as one travels from the source of sound, the decibel levels are different. The outdoor decibel levels have a larger decibel drop than the same distant measurements indoors. The outdoor measurement have a larger drop in decibels than when indoors, probably because of the sound reflective qualities of the concrete masonry 47 unit walls and concrete floor within the room where the testing was done. Therefore one can conclude that sound will dissipate in a shorter distant when outdoors in comparison to an enclosed room. There are also differences in decibel levels when the tool is applied to wood in comparison to when the tool is just running and not applied to wood. Tools that actually cut wood, such as the circular saws and the reciprocating saw, had a significant increase in decibel levels when cutting wood in comparison to when the tool was turned on and not cutting wood. Other tools such as the belt sander had a higher decibel levels when the tool was just running compared to when the tool was actually applied to wood. The router decibel levels were essentially equal when simply running and when applied to wood. Therefore when the sound level emissions of a tool are being evaluated, the tool should be tested with the power turned on and not applied to wood, and when the tool is turned on and applied to wood. In the evaluation of the study there is a very clear conclusion, there are very apparent dangers that exist pertaining to potential hearing loss with the use of power tools. All of the conventional portable carpenter power tools exceeded the decibel level that would classify the tool as safe, except for the drill which was the only tool evaluated that was battery powered. Therefore all workers working on a jobsite where power tools are being used (almost all jobsites) should be aware of the danger of permanently damaging their hearing, and take the proper precautions of protecting against that danger. CHAPTER 6 RECOMMENDATIONS Practice recommendations. Contractors and workers need to be more aware of the dangers of elevated noise levels on construction projects in order to stop the excessive amount of hearing damage among construction workers. Contractors need to constantly test the jobsites. Signs should be posted that communicate to the workers the dangers of the noise levels on the jobsite, and the benefits of wearing hearing protection. For example a sign may suggest that workers wear hearing protection all the time, or that hearing protection be worn when specific tools are operating and the workers are within stipulated distances of the operating tools. By listing the decibel levels of listed tools workers will begin to understand the decibel levels that are dangerous and what tools put them at risk. The safest practice though would be to incorporate hearing protection into the jobsites, the way work boots and hard hats are currently used on jobsites. There are no large jobsites in the country where a worker can walk onto the project without a pair of work boots and a hard hat. This is true for two reasons, the workers well being and the reduced cost of insurance for the contractor. The same should be true for hearing protection. It is well established that there is high risk of hearing damage on a construction jobsite, and there is an easy way to prevent damage, by wearing hearing protection. If the workers have better hearing not only is it better for their health, but it 48 49 creates a safer jobsite. Imagine the danger if a worker cannot hear a warning or instructions in a critical situation. In the author’s opinion, to ensure the safety of workers in construction, hearing protection should be worn at all times on the jobsites. There are several options for hearing protection. The most popular form of hearing protection on many jobsites is expandable foam plugs. The plugs are disposable and are only used once before being thrown away. The plugs are made from a foam material that is rolled or squeezed and then placed in the user’s ear. Once in the ear, the foam expands to fit the individual’s ear, and protects against noise. Pre-molded reusable plugs are an option as well; these plugs are made from a hard rubber or plastic material. These plugs are intended for numerous uses and are intended for repeated use. The plugs come in various sizes to provide the best fit. Earmuffs are another option of hearing protection, the earmuffs entirely cover the ears of the workers and completely block out sound. The muffs are mounted on a head band and some can be affixed directly to the hard hat. The earmuffs are a very effective form of hearing protection, but many workers complain that the earmuffs can be hot and cumbersome. The last option in hearing protection is canal caps. Canal caps are small plugs that are placed in the ears. The plugs are attached to a hard plastic band so that when not being used the worker can comfortably place the caps around his or her neck. All of these hearing protection options will protect the worker from permanent hearing damage. The best option is the one that the worker will wear. The contractor should ask his/her employees which hearing protection is most comfortable to the workers, so the workers will be more likely to wear the hearing protection.1 1 http://www.cdc.gov/niosh/topics/noise/ 50 Research recommendations. There are numerous studies that should be performed to better understand the vastly misunderstood subject of hearing safety within the construction industry. A study should be performed that would identify the current methods that contractors use to ensure that their workers’ hearing is protected. This includes the methods the contractors use to reduce noise on their projects as well the programs that are implemented to promote the wearing of hearing protection by the workers. A study should be performed that measures the decibel levels on actual jobsites. This would enable the evaluation of noise levels on jobsites and increase the knowledge of noise levels on jobsites, which could potentially increase the level of safety for the workers. A study should be performed that tests worker’s hearing in the construction industry. New workers’ hearing should be tested and compared to the tested hearing of veteran construction workers. The veteran construction workers’ hearing should also be compared with the hearing test data of the general population of the same age group. Therefore any difference in hearing between the new construction workers and the older construction workers can be determined if it is due to age or work environment. A survey of construction workers should be performed that would question their understanding of the dangers of noise levels on the jobsite. The survey should also question the workers about which form of hearing protection the workers are most comfortable wearing. LIST OF REFERENCES Asfahal, C. Ray, Industrial Safety and Health Management. Upper Saddle River, NJ: Prentice Hall, 2004 Beranek, L.L. Noise and Vibration Control Engineering Principles and Applications. Toronto: John Wiley & Sons Brooks, Christopher. Architectural Acoustics. Jefferson, NC: Brooks, 2003 Egan, David M. Architectural Acoustics. NY: McGraw Hill 1988 Goetsch, David L. Occupational Safety and Health for Technologists, Engineers, and Managers. Upper Saddle River, NJ: Prentice Hall, 1996 Harris, Cyril. Handbook of Acoustical Measurements and Noise Control. New York: McGraw Hill, 1991 Herrinton, Thomas N. Occupational Injuries Evaluation, Management, and Prevention. New York: Mosby, 1995 Kutruff, Heinrich. Room Acoustics: London: Spon, 2002 Mechel, Fridiolin. Formulas of Acoustics. Berlin: Springer, 2002 National Institute for Occupational Safety and Health, January 15, 2004. http://www.cdc.gov/niosh/pdfs/2001-157.pdf National Institute for Occupational Safety and Health, January 15 2004. http://www.cdc.gov/niosh/topics/noise/ Occupational Safety and Health Administration, January 16, 2004. http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARD S&p_id=10625 Radio Shack, January 17, 2004. www.radioshack.com 51 BIOGRAPHICAL SKETCH The author of this thesis, Gregory D. Callahan, is completing his Master of Science in Building Construction degree at the University of Florida. The author began his studies at the University of Florida in August of 2002. Prior to attending graduate school Mr. Callahan received a Bachelors of Art from Boston College in 1996. At Boston College the author’s major was art history. 52