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Hearing Science Intro Handout deJonge Page 1 of 13 Card number_____ 1 card fld "Info" SYLLABUS FOR HEARING SCIENCE Course Number CD 5707 Instructor Dr. de Jonge, Mar 58, 660-543-8809, [email protected], [email protected] Text Durrant & Lovrinic, Bases of Hearing Science, 3rd Edition Exams: One mid-term (multiple choice) and one final exam (short answer). Paper: A paper is required. The purpose of the paper is for you to demonstate your knowledge of cochlear physiology. Basically, you should explain the functioning of the inner ear and VIII Nerve. Explain normal auditory functioning and, when appropriate, contrast it with changes that occur with disorders (Ménière's disease, acoustic neuroma, noiseinduced hearing loss, etc.). Follow APA style. Scope: The scope of the course is the structure and function of the auditory periphery. The primary emphasis is upon cochlear anatomy and physiology. In other words, we try to explain how the normal ear works, and how hearing disorders may change these processes. At the end of the course (second half) there is a review of physical concepts, acoustics, and the measurement of sound. This should help you to appreciate auditory processes. Attendance: Class attendance policy is consistent with University policy. In addition, four absences are allowed for whatever reason (approved or not, at your discretion). Beyond this the final grade is reduced by 1/4 of a letter grade for each additional absence. The final grade will be increased by 1/4 for each of the allowed absences that is not used. Perfect attendance improves performance by one full letter grade. TOPICS I. Cochlear mechanics: The basic topic here involves basilar membrane movement, explaining how the cochlea carries out its frequency analysis, and how this relates to theories of hearing. Read chapter 5. II. Cochlear electrophysiology: This section deals with the electrical events occurring in the inner ear, and the role they play in generating the 8th nerve response. This material is very basic to an understanding of brainstem audiometry. Read chapter 5. III. Neural encoding: This section covers current thinking on how the auditory system (at the level of the 8th nerve and brainstem) encodes sensory information and processes it. Relations to such topics as binaural hearing, localization, etc. are discussed. Read chapter 6. MIDTERM EXAMINATION IV. A basic review of physical concepts: Physical concepts which relate to understanding how the ear behaves, acoustics, and the measurement of sound. This section is basically, "go at your own speed." Study questions are handed out for each chapter, which you can answer, Hearing Science Intro Handout deJonge Page 2 of 13 and questions you may have are dealt with in class. After you have had a chance to work the problems, answer sheets will be handed out. At the end of each chapter, there will be a practice quiz, and answer sheets will also be available for these. Questions on the final will be similar to those on the problems and quizes. No surprises. Formal lecture will include major topics in each of the chapters. Read chapters 1, 2, and 3. V. Anatomy of the ear: This is a general review of the anatomy, primarily of the inner ear, but also including the central auditory pathway. A HyperCard stack is available for drill. The matching part of the final will be based upon this tutorial. Read chapter 4. FINAL EXAMINATION Practical (see stack Anatomy Pics II) & Short Answer card fld "Paper Topics…" The purpose for doing the paper is for you to develop an understanding of how the ear works. The depth and quality of your understanding is assessed by how well you can express your knowledge in print using text, figures, and tables. The length of the paper should be about 20 double-spaced typed pages (5,000 words). Concepts that should be included in the paper… •In general, look at the ear as if it were a machine; explain how the machine works •anatomy of the periphery (inner ear, including organ of Corti, and its innervation), and central auditory system ◊main focus on periphery •basilar membrane mechanics, traveling wave theory •hair cell physiology, neural innervation of hair cells •motility of OHCs •neural tuning curves, role of the OHCs in sharpening mechanical response, OAEs •cochlear electrophysiology, role of the ◊CM, EP, SP, generator potential, AP ◊H. Davis' model of the transducer action of the hair cells within cochlea •Events involved in generating the neural impulse, and its propagation ◊explain how the BM motion causes the neural impulse •Major theories of hearing relating to pitch and loudness ◊place theory, tonotopicity ◊frequency theory ◊volley theory ◊encoding loudness •Where possible, show how the basic principles you are describing relate to common pathologies, or diagnostic procedures like: NIHL, Ménière's disease, acoustic nerve tumors, electrocochleography, ABR, OAEs, etc. For example, salicylate intoxication reduces OHC turgor, causing a temporary sensorineural hearing loss. Hearing Science Intro Handout deJonge Page 3 of 13 Style and Format Issues •Create an outline for your paper ◊Use the outline for making headings and subheadings •APA style is only a guide. APA is primarily for creating a copy manuscript to be submitted to a journal's editor. You want to create a finished manuscript, like what would appear in print. ◊Use the formatting of the American Auditory Society's journal, Ear and Hearing, as a guide. •Use general, summary chapters in major texts… ◊Experiments in Hearing, Békésy ◊Foundations of Modern Auditory Theory, J.V. Tobias ◊The Auditory Periphery, Peter Dallos ◊etc. •Include figures and tables… ◊tables are easily created using MS Word ◊become familiar with a graphics program for creating figures (like MS PowerPoint or Word) ◊learn how to use a spreadsheet program to create charts (like MS Excel) ◊learn to use a scanner and its associated software to include existing images (like ScanSuite) ◊learn how to use a program like Adobe Photoshop (or PhotoImpact) to modify the scanned image ◊learn how to merge the figure into your word processing document (like MS Word) Everything you need (scanner and software) is on the Dell PCs in room 61. Plagiarism 1. To use and pass off as one's own (the ideas or writings of another). 2. To appropriate for use as one's own passages or ideas from (another). •Students tend to plagiarize, not so much to be dishonest, but because they have trouble expressing themselves. •Don't string together paragraphs, largely unmodified. Even if you cite the author, it is still plagiarism. card fld "Major Topics…" For the first half of the class, dealing with cochlear mechanics and electrophysiology… -see stack Traveling Wave Mid-Term Major topics for first three chapters in Durrant & Lovrinic Chapter 1: Physical concepts ◊impedance, Ohm's Law -stack Ohm's Law Hearing Science Intro Handout deJonge ◊vector addition -stack dB Calculator & More ◊Hooke's Law -stack Hooke's Law ◊free and forced vibration ◊damping -stack Damping ◊projected uniform circular motion -stack Harmonic Motion Chapter 2: Acoustics ◊Helmholtz resonator -at end of stack Hooke's Law ◊inverse square law -in stack dB Calculator & More ◊resonance properties of tubes -stack Tube Resonance Chapter 3: Measurement of Sound ◊decibel -in stack dB Calculator & More ◊additions of pure tones to form complex sounds -stack Oscilloscope ◊adding (combining) complex sounds -in stack dB Calculator & More ◊spectrum level, octave band level, overall level -in stack dB Calculator & More ◊spectral analysis ◊spectra of tone bursts vs. clicks Basic Anatomy… Self-paced tutorial, quiz -in stack Anatomy Pics II Final Exam Hearing Science Study Questions: Chapter 1 Page 4 of 13 Hearing Science Intro Handout deJonge Page 5 of 13 1. Why is is that "People who cannot cope with mathematics are not fully human; being a subhuman variety that have learned to wear shoes, bathe, and not make messes in the house…?" --Lazarus Long 2. Describe quantification. Why is it important, or useful? State, in words, what scientific notation is. Then express the following numbers in scientific notation: (e.g. 100 = 10 2; 1000 = 1.0 x 103 3. a. 100,1000 b. 52380,13760000 d. 0.0002,0.0315 e. 41967,.01023 Why is scientific notation useful? 4. c. 0.00531, 0.1 f. 0.000642,0.36 Using this notation, multiply each of the above pairs of numbers. Now divide each pair. (Eg: 100/1000 = 10 (2-3) = 10-1. 5. What is a vector? A scalar? Give examples of each. Choose any two vectors you like and try adding them. 6. What are the five elements of quantification? 7. How does weight differ from mass. Give an example. 8. What are the units of: velocity, acceleration, force, and momentum in the MKS system? The CGS system? 9. What are Newton's three laws of motion? 10. Describe Hooke's Law, first in words, then in an equation. What is the "modulus of elasticity"? 11. What is resistance? Describe the relationship between force, velocity, and resistance. Can you describe how this relates to electricity? 12. How is power related to energy and work? Try to give a common everyday example. 13. How could you use a spring, mass, and friction element to illustrate simple harmonic motion. How does this relate to a sine wave? 14. What are the frequencies that have these periods: a. 0.1 sec b. 0.001 sec c. 0.125 sec d. 5 msec 15. Calculate the angular velocity for these frequencies: a. 1000 Hz b. 62 Hz c. 540 Hz d. 8 Hz 16. Free vibration, mass, stiffness, and natural frequency: what do they all have in common? 17. How does the resonant frequency relate to the natural frequency. 18. Describe what impedance means. Use impedance to describe what happens when forced vibration occurs at a frequency other than the resonant frequency. 19. Draw a graph that illustrates damping. Plot amplitude as a function of time. 20. Is impedance a vector or a scalar quantity? If you knew the mass, stiffness, and resistance could you calculate the impedance of this system? Hearing Science Intro Handout deJonge Page 6 of 13 Hearing Science Study Questions: Chapter 1 Answers to Selected Questions 3. State, in words, what scientific notation is. Then express the following numbers in scientific notation: (e.g. 100 = 10 2; 1000 = 1.0 x 103) a. 1.0 x 102 ,1.0 x 103 b. 5.238 x 104,1.376 x 107 c. 5.31 x 10-3, 10-1 d. 2 x 10-4,3.15 x 10-2 e. 4.1967 x 104,1.023x 10-2 f. 6.42 x 10-4,3.6x10-1 Why is scientific notation useful? It saves space, enhances estimation. 4. Using this notation, multiply each of the above pairs of numbers. Now divide each pair. (Eg: 100/1000 = 10(2-3) = 10-1. a. 105,10-1 b. 7.2 x 1011, 3.8 x 10-3 c. 5.31 x 10-4,5.31x10-2 d. 6.3x10-6, 6.3 x 10-3 e. 4.29 x 102, 4.1 x 106 f. 2.31 x 10-4, 1.78x10-3 5. What is a vector? A scalar? Give examples of each. Choose any two vectors you like and try adding them. A vector has magnitude and direction, a scalar has only magnitude 7. How does weight differ from mass. Give an example. Weight is Force. Pounds are actually units of force. As an example, consider your weight vs. mass on the earth as opposed to the moon. 8. What are the units of: velocity, acceleration, force, and momentum in the MKS system? The CGS system? velocity, v = m/sec or cm/sec acceleration, a = m/sec2 or cm/sec2 Force, F = ma = kg m/sec2 or gm cm/sec2 (Newtons, N or dynes) Momentum = Fv = N-m or dyne-cm (Note, this "-" is a hyphen, not a minus symbol, N-m is Newtons times meters) 10. Describe Hooke's Law, first in words, then in an equation. What is the "modulus of elasticity"? The extension is proportional to the tension. F = -kx. The variable, k, is the modulus of elasticity. 11. What is resistance? Describe the relationship between force, velocity, and resistance. Can you describe how this relates to electricity? Resistance = Force / velocity. This is Ohm's Law 12. How is power related to energy and work? Try to give a common everyday example. Power is the rate at which energy is dissipated, measured in Watts. A watt is 1 joule/sec. Work is the same thing as energy. A 40 watt light bulb consumes 40 joules of energy each second. 13. How could you use a spring, mass, and friction element to illustrate simple harmonic motion. How does this relate to a sine wave? See the diagram for question 20. SHM is the sort of motion this system undergoes. 14. What are the frequencies that have these periods: a. 0.1 sec b. 0.001 sec 10 Hz 1000 Hz c. 0.125 sec 8 Hz d. 5 msec 200 Hz Hearing Science Intro Handout 15. deJonge Calculate the angular velocity for these frequencies: a. 1000 Hz b. 62 Hz 6280 radians/sec 2448 radians/sec Page 7 of 13 c. 540 Hz 3392 radians/sec d. 8 Hz 50 radians/sec (Hint angular velocity, = 2πf, t is an angle, measured in radians. The equation for a sine wave is y = A sin ( t). ) 16. Free vibration, mass, stiffness, and natural frequency: what do they all have in common? A system in free vibration vibrates at its natural frequency, = (k/m).5 17. How does the resonant frequency relate to the natural frequency. Same thing, except the resonant frequency is for forced vibration. 18. Describe what impedance means. Use impedance to describe what happens when forced vibration occurs at a frequency other than the resonant frequency. Impedance is the ratio of a "Force-like" quantity to a "Flow-like" quantity. At resonance, the impedance of the system is at a minimum since it is purely resistive, reactance is zero. 19. Draw a graph that illustrates damping. Plot amplitude as a function of time. I will show you a computer simulation that illustrates this. There is a graph in your text. 20. Is impedance a vector or a scalar quantity? If you knew the mass, stiffness, and resistance could you calculate the impedance of this system? Z is a vector quantity. | Z | = ( R2 + ( M - k/)2 ).5, = tan-1 (X/R) where M = mass, k = stiffness, R = resistance, X = reactance( M - k/), = phase angle, = 2πf Hearing Science Quiz Chapter 1: Physical Concepts 1. 2. 3. 4. 5. 6. Express the following numbers as ten raised to some power: a. 1 b. 1000 d. 0.1 e. 0.010 Express the following numbers in scientific notation: a. 3.14159 b. 231 c. 0.015 Perform the following multiplications: a. 102 x 103 b. 105 x 10-3 c. (4 x 106) x (3 x 10-1) Perform the following divisions: a. 102 / 103 b. 105 / 10-3 c. (4 x 106) / (3 x 10-1) Convert seconds to msec or vice-versa a. 1 sec b 1.5 sec c. 1.5 msec Convert Hz to KHz or vice-versa a. 1000 Hz b. 10 KHz c. 0.5 KHz 7. What are the frequencies that have these periods: a. 0.01 sec b. 1 msec 8. c. 10000 f. .001 What are the periods for these frequencies? c. 2 msec Hearing Science Intro Handout a. 4000 Hz 9. 10. deJonge b. 125 Hz Page 8 of 13 c. 2.0 KHz Calculate angular velocity for each of these frequencies: a. 1000 Hz b. 2 KHz c. 500 Hz Are the following quantities vectors or scalars? a. mass b. temperature d. velocity e. impedance c. force f. speed 11. This question relates to Ohm's law as it applies to acoustics: P (pressure), Z (impedance), U (volume velocity). What happens to a. U if Z decreases and P stays the same b. Z if U increases while P stays the same c. P if Z stays the same and U increases 12. A spring is attached to a mass of 1.0 kg and the pull of gravity (9.8 m/sec 2) causes the spring to extend 0.5 m. a. What is the modulus of elasticity for the spring? b. If you were to pull down the mass an additional few centimeters, when you let in go it would "bounce up and down." How many times would it bounce up and down within one minute? c. What would be the time interval between succcessive bounces? Hearing Science Quiz Chapter 1: Physical Concepts: Answers 1. 2. 3. Express the following numbers as ten raised to some power: a. 101 b. 103 c. 104 -1 -2 d. 10 e. 10 f. 10-3 Express the following numbers in scientific notation: a. 3.14159 x 100 b. 2.31 x 102 c. 1.5 x 10-2 Perform the following multiplications: a. 105 b. 102 c. 1.2 x 10-6 Perform the following divisions: a. 10-1 b. 10-2 c. 1.33 x 107 Convert seconds to msec or vice-versa a. 1000 ms b 1500 ms c. 0.0015 sec Convert Hz to KHz or vice-versa a. 1 kHz b. 10000 Hz c. 500 Hz 7. What are the frequencies that have these periods: a. 100 Hz b. 1000 Hz c. 500 Hz 4. 5. 6. 8. 9. 10. What are the periods for these frequencies? a. 0.25 ms b. 8 ms c. 0.5 ms Calculate angular velocity for each of these frequencies: a. 6280 rad/sec b. 12560 rad/sec c. 3140 rad/sec Are the following quantities vectors or scalars? a. scalar b. scalar d. vector e. vector c. vector f. scalar Hearing Science Intro Handout deJonge Page 9 of 13 11. This question relates to Ohm's law as it applies to acoustics: P (pressure), Z (impedance), U (volume velocity). What happens to a. U increases b. Z decreases c. P increases 12. A spring is attached to a mass of 1.0 kg and the pull of gravity (9.8 m/sec2) causes the spring to extend 0.5 m. a. 19.6 N/m b. 0.7 Hz x 60 = 42 times per minute c. 1.419 seconds between succcessive bounces Hearing Science Study Questions: Chapter 2 1. Describe how Boyle's experiment revealed the necessity of a medium to transmit sound. How did his experiment relate to impedance mismatch? (Note: this is related to an understanding of the impedance matching characteristics of the middle ear.) 2. What are the units for density? How is it related to condensation and rarefaction? 3. Define longitudinal and transverse wave? Which type of wave is sound? 4. How is the speed of sound affected by the elastic modulus (k), density ( ), frequency (f), temperature (T), static pressure (P o)? 5. What is the wavelength () of a 1000 Hz tone in air? In hydrogen? In fresh water? Express in meters. 6. As a sound wave travels from the atmosphere into the ear canal, what happens to its wavelength? (Hint: temperature) 7. What is the inverse square law? If you were 10 feet from a loudspeaker, how far away would you have to move to reduce the intensity by 50% 8. What is the characteristic impedance of a medium, like air? How is it related to intensity and sound pressure? 9. What is the intensity of a tone whose pressure is 2 x 10 -3 N/m2? 10. Describe what happens when sound travels from an air filled to a water filled medium. 11. What is the difference between an anechoic chamber and a soundproof medium? 12. Describe what is meant by the reverberation time. How is the reverberation time related to volume and absorption? 13. Describe a Helmholtz resonator. What happens to the fundamental frequency as you change the length of its neck? The diameter? The volume of the cavity? 14. Contrast resonance occurring in a pipe closed at one end with a pipe open at both ends. What would be the resonant frequency for a tube closed at one end with a length of 2.25 cm? Answers to Selected Questions from Hearing Science Study Questions: Chapter 2 1. Describe how Boyle's experiment revealed the necessity of a medium to transmit sound… 2. What are the units for density? How is it related to condensation and rarefaction? = gm/cm3, or kg/m3, condensation means an region in The results of Boyle's experiment stemmed from the reduction in density of the propagating medium, the characteristic impedance of the propagating medium Zc = oc. the wave where the > o, rarefaction is < o Hearing Science Intro Handout 4. deJonge Page 10 of 13 How is the speed of sound affected by the elastic modulus (k), density (), frequency (f), temperature (T), static pressure (P o)? To increase c you could increase k, Po, T, or reduce . f has no effect. 5. What is the wavelength () of a 1000 Hz tone in air? .343 m. In hydrogen? 1.27 m. In fresh water? 1.481 m. Express in meters. 6. As a sound wave travels from the atmosphere into the ear canal, what happens to its wavelength? (Hint: temperature) It gets larger. 7. What is the inverse square law? The intensity is inversely proportional to the square of the distance from the source. If you were 10 feet from a loudspeaker, how far away would you have to move to reduce the intensity by 50%? 14.1 feet from the sound source. 8. What is the characteristic impedance of a medium, like air? Zc = oc How is it related to intensity and sound pressure? I = p2/Zc 9. What is the intensity of a tone whose pressure is 2 x 10 -3 N/m2? About 10-8 W/m2 11. What is the difference between an anechoic chamber and a soundproof medium? Anechoic implies no echos, soundproof reduced noise level. 12. Describe what is meant by the reverberation time. RT measures the amount of time it takes sound to decay to a value 0.1% of its original magnitude (a reduction of 60 dB in the SPL). How is the reverberation time related to volume and absorption? RT increases with volume, reduces with increased absorption. Hearing Science Quiz Chapter 2: Acoustics 1. What is the formula which relates wavelength and frequency to the speed of sound? 2. If the speed of sound is 344 m/sec then what would the wavelength of a 125 Hz tone be? What would be the frequency of a tone with a wavelength of .344 meters? 3. You are standing 20 feet from a sound source and the intensity is 100 dB SPL. How far away would you have to move to reduce the level to 88 dB? Does the inverse square law "work" inside of a building such as a factory? 4. At a distance of 8 feet a sound source is producing a certain intensity. How far away would you have to move from the source in order for the intensity to be reduced to 37% of its original level? 6. What is a Helmholtz resonator? How can you vary the frequency that it will resonate to? 7. You have a pipe open at one end and closed at the other. If the pipe is 0.5 meters long, what frequency will it resonate to? If you had the same pipe but both ends were open, what frequency will it resonate to? 8. With reference to the previous question, is it possible to have a tube that is "partially open" or "partially closed"? How would this affect the response of the tube? What is the characteristic impedance of a tube and who cares? Hearing Science Answers to Selected Questions Quiz Chapter 2: Acoustics 1. What is the formula which relates wavelength and frequency to the speed of sound? f = c 2. If the speed of sound is 344 m/sec then what would the wavelength of a 125 Hz tone be? 2.752 m. What would be the frequency of a tone with a wavelength of .344 meters? 1000 Hz 3. You are standing 20 feet from a sound source and the intensity is 100 dB SPL. How far away would you have to move to reduce the level to 88 dB? 80 feet from the source. Does the inverse square law "work" inside of a building such as a factory? Only within a restriced distance from the sound source. Hearing Science Intro Handout deJonge Page 11 of 13 4. At a distance of 8 feet a sound source is producing a certain intensity. How far away would you have to move from the source in order for the intensity to be reduced to 37% of its original level? distance = (8 2/.37).5 = 13.1 feet. 6. What is a Helmholtz resonator? An acoustical spring-mass system. How can you vary the frequency that it will resonate to? Change length or diameter of the neck, or the volume of the cavity. 7. You have a pipe open at one end and closed at the other. If the pipe is 0.5 meters long, what frequency will it resonate to? 172 Hz. If you had the same pipe but both ends were open, what frequency will it resonate to? 344 Hz 8. With reference to the previous question, is it possible to have a tube that is "partially open" or "partially closed"? Yes. How would this affect the response of the tube? It changes the height of the resonant peaks. What is the characteristic impedance of a tube and who cares? Zc = oc/A. This characteristic of tubes influences ear canal resonances and hearing aid responses. Hearing Science Study Questions: Chapter 3 1. What are the rms values of these sine waves? a. 1.0 Volt (peak) b. 3.0 V (peak-to-peak) c. 0.02 dyne/cm2 (peak) 2. What is the purpose of using a dB scale? (Why bother?) 3. Mathematically, what is Fechner's Law? If C = 1 and the magnitude of the stimulus changed from 10 to 100. How would the response change? 4. Convert these intensities or sound pressures to IL or SPL: a. 10-12 W/m2 b. 2 x 10-6 W/m2 2 d. 2 x 10-4 N/m e. 0.02 N/m2 c. 4.1 x 10-4 dyne/cm2 f. 634 µPa 5. Explain why 60 dB IL equals 60 dB SPL. 6. The microphone of a hearing amplifies a 1 millivolt signal to a level of 1.0 volt (in a hearing aid). What is the amplifier gain in dB? 7. The fundamental frequency is 500 Hz. What frequency is a. 2 octaves above it b. 1 ocatve below it d. 4 octaves below it e. the 7th harmonic c. 3 octaves above it 8. What are the three general classes of sounds? 9. Using a time window of 2 msec, sketch the graph that illustrates the combination of each of the following frequencies (assume that each wave begins with a phase of 0°): a. 500 Hz, Ap = 60 b. 1000 Hz, Ap = 30 c. 4000 Hz, Ap = 15 The combination of these waves should be a complex periodic sound. 10. Gaussian and white noise both refer to the same type of sound, but to two different aspects of it. Explain. 11. White noise has a spectrum level of 50 dB and a bandwidth that extends from 200 Hz to 6000 Hz. If you used a sound level meter to measure the overall level, what would be the dBC scale reading? 12. The same white noise as in #11 is input to an octave band filter centered at 1000 Hz. At what dB level does it exit the filter? At what level would it exit the filter if the center frequency was 2000 Hz? Define a. rise-decay time b. low-pass filter c. high-pass filter d. band-pass filter e. harmonic distortion f. phase distortion g. intermodulation distortion h. half-power bandwidth 13. Hearing Science Intro Handout 14. deJonge Page 12 of 13 Why is a 1000 Hz tone burst really not a pure-tone? What does this have to do AEP testing? Hearing Science Study Questions: Chapter 3 Answers to Selected Questions 1. What are the rms values of these sine waves? a. 1.0 Volt (peak) b. 3.0 V (peak-to-peak) .707 V 1.06 V c. 0.02 dyne/cm2 (peak) .014 dyne/cm2 2. What is the purpose of using a dB scale? (Why bother?) Basically, it compresses wide ranges of numbers, and anchors a zero point to a reference value 3. Mathematically, what is Fechner's Law? R= k log S If C = 1 and the magnitude of the stimulus changed from 10 to 100. How would the response change? It would double 4. Convert these intensities or sound pressures to IL or SPL: a. 10-12 W/m2 b. 2 x 10-6 W/m2 c. 4.1 x 10-4 dyne/cm2 d. 2 x 10-4 N/m2 e. 0.02 N/m2 f. 634 µPa 5. Explain why 60 dB IL equals 60 dB SPL. because a sound having a pressure of 2000 µPa (60 dB SPL) has an intensity of 10-6 W/m2 (60 dB IL) 6. A hearing aid amplifies a 1 millivolt signal from the microphone to a level of 1.0 volt. What is the amplifier gain in dB? dB = 20 log( 1/.001) = 60 dB 7. The fundamental frequency is 500 Hz. What frequency is a. 2 octaves above it b. 1 ocatve below it c. 3 octaves above it 2000 Hz 250 Hz 4000 Hz d. 4 octaves below it e. the 7th harmonic 31.25 Hz 3500 Hz 8. What are the three general classes of sounds? simple, complex periodic, and complex aperiodic We have a computer simulation that will do question 9. 10. Gaussian and white noise both refer to the same type of sound, but to two different aspects of it. Explain. Gaussian: randomness, white: all frequencies of the spectrum 11. White noise has a spectrum level of 50 dB and a bandwidth that extends from 200 Hz to 6000 Hz. If you used a sound level meter to measure the overall level, what would be the dBC scale reading? About 87.6 dB 12. The same white noise as in #11 is input to an octave band filter centered at 1000 Hz. At what dB level does it exit the filter? 78.5 dB At what level would it exit the filter if the center frequency was 2000 Hz? 3 dB higher 14. Why is a 1000 Hz tone burst really not a pure-tone? The duration is too short. What does this have to do AEP testing? We sacrifice frequency specificity to elicit synchronous firing from many nerve fibers. Hearing Science Quiz Chapter 3: Measurement of Sound Hearing Science Intro Handout deJonge Page 13 of 13 1. What is the rms value of a wave that has a peak voltage of 2.0 V? If the rms value of a wave is 1.0 V, then what is the peak value? If the peak-to-peak value is 5.0 V, then what is the rms value? 2. Convert the following sound pressures to dB SPL a. 20 µPa b. 2000 µPa c. 4.6 x 103 µPa 3. Convert the following dB SPLs to sound pressures in µPa a. 42 dB b. -10 dB c. 77 dB 4. Convert the following intensities (given in watts/m2) to dB IL a. 10-10 b. 2.5 x 10-8 c. 3.6 x 10-13 5. Convert the following dB ILs to intensities in watts/m2 a. 65 dB b. 72 dB c. 7 dB 6. Two complex tones are being combined? One is at a level of 27 and the other is at 44 dB SPL. What is the combined SPL? 7. A noise which has a bandwidth of 6000 Hz has an overall level of 90 dB SPL. What is the spectrum level? 8. The fundamental frequency of my voice is 125 Hz. What are the first, third and fifth harmonics? 9. How does the Heisenberg uncertainty principle relate to frequency specificity and time? Hearing Science Answers to Selected Questions Quiz Chapter 3: Measurement of Sound 1. What is the rms value of a wave that has a peak voltage of 2.0 V? 1.414 V If the rms value of a wave is 1.0 V, then what is the peak value? 1.414 V If the peak-to-peak value is 5.0 V, then what is the rms value? 1.768 V We will go over the problem of converting pressure & intensity to dB (and vice-versa) in class. There is a HyperCard stack that will allow you to check your own answers. 7. A noise which has a bandwidth of 6000 Hz has an overall level of 90 dB SPL. What is the spectrum level? 52.2 dB 8. The fundamental frequency of my voice is 125 Hz. What are the first, third and fifth harmonics? 125, 375, and 625 Hz 9. How does the Heisenberg uncertainty principle relate to frequency specificity and time? Short duration signals necessarily have a large bandwidth. Therefore, clicks used in ABR can not be frequency specific.