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Hearing Science Intro Handout
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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,
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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.
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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
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◊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
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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?
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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
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Calculate the angular velocity for these frequencies:
a. 1000 Hz
b. 62 Hz
6280 radians/sec
2448 radians/sec
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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.
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b. 125 Hz
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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
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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
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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.
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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.
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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.