SPPA 206: Hearing Science
Study Guide for Exam 1 (Physical Acoustics)
Notes: This study guide is intended to give you a general idea of some of the topics that might
be covered on the exam, and to help you organize your studying. It is not intended to cover all
of the topics that might appear on the exam. It is not designed as a substitute for studying
the readings and your lecture notes. You should also look over the study questions at the end
of the chapters you read. The exam will consist primarily of short answer, fill-in-the-blank,
multiple-choice questions, and fairly short explanations (there are many examples of these
below). You may also be asked to either make or label drawings.
1. Explain the events that are involved in the propagation of a sound wave.
2. Draw time- and frequency-domain representations of simple periodic, complex periodic,
complex aperiodic, long-ish variety, and transient (i.e., complex aperiodic, short-ish type)
sounds.
3. Draw time- and frequency-domain representations of two complex periodic sounds with
different fundamental frequencies.
4. Draw two different vowels spoken at about the same fundamental frequency, and the same
vowel spoken at two different fundamental frequencies.
5. Draw time-domain representations of two simple periodic sounds with the same frequency
and phase, but different amplitudes.
6. Draw time-domain representations of two simple periodic sounds with the same frequency
and different amplitudes but different phases.
7. Draw amplitude spectra of two sounds with the same fundamental frequencies but different
spectrum envelopes.
8. Draw amplitude spectra of two sounds with different fundamental frequencies but similar
spectrum envelopes.
9. Calculate signal frequencies for sinusoids with the following values:
a. period = 0.34 s (seconds)
b. period = 2 s
c. period = 10 ms (milliseconds)
d. period = 2 ms
e. wavelength = 20 cm
f. wavelength = 100 cm
SPPA 206, Study Guide for Exam 1 (17 February 2016)
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Answers:
a. f = 1/0.34 = 2.94 Hz
b. f = 1/2 = 0.5 Hz
c. f = 1/0.01 = 100 Hz
d. f = 1/.002 = 500 Hz
e. f = c/WL (speed of sound/wavelength) = 35000/20 = 1750 Hz
f. f = c/WL (speed of sound/wavelength) = 35000/100 = 350 Hz
10. Calculate the three lowest resonant frequencies of the following uniform tubes that are
closed at one end and open at the other end:
a. 10 cm
b. 30 cm
c. 40 cm
Answers:
a.
wavelength of lowest resonance = 40 cm (10 x 4)
f = 35000/40 = 875
R1 = 875 (R1 = frequency of resonance number 1)
R2 = 2625
R3 = 4375
b.
wavelength of lowest resonance = 120 cm (30 x 4)
f = 35000/120 = 291.7
R1 = 291.7
R2 = 875.0
R3 = 1458.3
c.
wavelength of lowest resonance = 160 cm (40 x 4)
f = 35000/160 = 218.75
R1 = 218.75
R2 = 656.25
R3 = 1093.75
11. Show what the frequency-response curves look like for the tubes in the problem above.
12. A complex periodic signal has a fundamental period of 4 msec. What is the fundamental
frequency of the signal? At what frequencies would we expect to find energy?
13. How are the terms octave and harmonic different? A harmonic progression is
(linear/logarithmic) while an octave progression is (linear/logarithmic). In general, how are
linear and logarithmic progressions different from one another?
SPPA 206, Study Guide for Exam 1 (17 February 2016)
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14. Give examples of the following kinds of graphs, being sure to label both axes:
a.
b.
c.
d.
amplitude spectrum
phase spectrum
frequency-response curve
time-domain representation
15. Give a brief explanation of the basic idea behind Fourier analysis. What is the input to
Fourier analysis and what kind of output(s) does it produce?
16. Draw and label frequency-response curves for low-pass, high-pass, and band-pass filters.
17. What parameters control the frequency of vibration of a spring and mass system?
18. Draw the time domain representation of one cycle of a sinusoid as variations in
instantaneous air pressure over time and one cycle of that same sinusoid as variations in
instantaneous velocity over time.
19. How, if at all, are the terms resonant frequency and harmonic different?
20. How, if at all, are the terms resonant frequency and formant different?
21. A harmonic is a peak in: (a) a frequency response curve, (b) an amplitude spectrum, or (c)
either a frequency response curve or an amplitude spectrum.
22. A resonance is a peak in: (a) a frequency response curve, (b) an amplitude spectrum, or (c)
either a frequency response curve or an amplitude spectrum.
23. A formant is a peak in: (a) a frequency response curve, (b) an amplitude spectrum, or (c)
either a frequency response curve or an amplitude spectrum.
24. A frequency response curve describes a _________________________.
25. An amplitude spectrum describes a _________________________.
26. Draw the frequency response curves for two band-pass filters that differ only in center
frequency.
27. Explain how a bank of band-pass filters could be used to measure the amplitude spectrum
of a time domain signal.
28. For the question above, to get the most accurate estimate of the amplitude spectrum,
should the band-pass filters that comprise the filter bank be narrow band or wide band?
Explain your answer. Should there be a large number of closely spaced filters or a small
number of widely spaced filters? Explain your answer.
SPPA 206, Study Guide for Exam 1 (17 February 2016)
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Some Terms for Exam 1 (Physical Acoustics)
exponent
exponential notation
logarithm
linear
time domain/frequency domain
sine wave/sinusoid/pure tone
types of sound: simple periodic, complex periodic, complex aperiodic (noise & transient)
spectrum envelope
amplitude envelope
harmonic
octave
displacement
cycle
period
fundamental period
fundamental frequency
wavelength
phase
instantaneous amplitude
overall amplitude
peak-to-peak amplitude
velocity
sound propagation
compression
rarefaction
atmospheric pressure
Fourier analysis
amplitude spectrum
phase spectrum
filter
frequency response curve
center frequency
bandwidth
resonance
forced vibration
filter types: high pass, low pass, band pass
acceleration
velocity
power
intensity
force
work
pressure