Chapter 15 – Sound Review
Name: __________________
LT# 1: Relate the properties of sound waves to the way we perceive sound.
1. Sound is a ___________ wave.
2. True/False
____a. The fastest which sound can move is when it is moving through a vacuum.
____b. If all other factors are equal, a sound wave will travel fastest in the most dense materials.
____c. A loud shout will move faster through air than a faint whisper.
____d. Sound waves would travel faster on a warm day than a cool day.
____e. A high pitched sound has a low wavelength.
____f. Two different guitar strings are used to produce a sound. The strings are identical in terms of
material, thickness and the tension to which they are pulled. Yet string A is shorter than string B.
Therefore, string A will produce a lower pitch.
____g. Doubling the frequency of a sound wave will halve the wavelength but not change speed of the
wave.
____h. Beats result when two sounds of slightly different frequencies interfere.
____i. Two tuning forks have 252 Hz and 257 Hz. A beat frequency of 5 Hz will be heard.
3. A tuning fork of frequency 384 Hz is sounded at the same time as a guitar string. Beats are observed;
exactly 30 beats are heard in 10.0 s. The frequency of the string in hertz is ____.
a. 38.4
b. 354 or 414
c. 369 or 399
d. 374 or 394
e. 381 or 387
LT #2: Solve problems relating the frequency, wavelength, and velocity of sound.
4. A vibrating object with a frequency of 200 Hz produces sound which travels through air at 360 m/s.
The number of meters separating the adjacent compressions in the sound wave is ____.
5. A sound wave traveling at a speed of 340 m/s has a wavelength of 2.5 m. What is the pitch of the
sound?
6. What is the wavelength of a sound wave with the same pitch as in problem 5 but is traveling through
water at 1435 m/s?
7. A note on a piano has a pitch of 65 Hz, assume fundamental frequency. What is the pitch of the note
that is one octave/harmonic higher?
8. What is the wavelength of a sound made by a violin string vibrating at 340 Hz if the wave is traveling
at 350 m/s?
LT #3: Understand resonance, especially how it is applied to strings and air columns.
10. True/False
____a. A standing wave pattern is formed as a result of the interference of two or more waves.
____b. A standing wave pattern is a regular and repeating vibrational pattern established within a
medium; it is always characterized by the presence of nodes and antinodes.
____c. A musical instrument can play any frequency imaginable.
____d. All musical instruments have a natural frequency or set of natural frequencies at which they will
vibrate; each frequency corresponds to a unique standing wave pattern.
____e. The fundamental frequency of a guitar string is the highest frequency at which the string
vibrates.
____f. The fundamental frequency of a guitar string corresponds to the standing wave pattern in which
there is a complete wavelength within the length of the string.
____g. If the fundamental frequency of a guitar string is 200 Hz, then the frequency of the second
harmonic is 400 Hz.
____h. Longer air columns will produce lower frequencies.
____i. The pitch of a sound can be increased by shortening the length of the air column.
11. If you shorten the string on a guitar to 0.2 m. What is the pitch of the note?
12. You play a 300 Hz note in a tube that is closed at one end. What is the pitch if you open the tube at
both ends?
13. If the fundamental frequency is 20Hz, then the 2nd harmonic
a) on a string is _________Hz
b) In an open pipe is _________ Hz
14. If there is a closed pipe and the first harmonic or the fundamental resonant sound is heard at .10 m
length, find the frequency of the tuning fork. Use the speed of sound as 343m/s.
15. If there is an open pipe and the length between two consecutive octaves is 2 m. Find the frequency
of the tuning fork producing the standing waves.
16. A 20-cm long pipe is covered at one end in order to create a closed-end air column. A vibrating
tuning fork is held near its open end, forcing the air to vibrate in its first harmonic. The wavelength of
the standing wave pattern is ____.
a. 5 cm
b. 10 cm
c. 20 cm
d. 40 cm
e. 80 cm
17. A stretched string vibrates with a fundamental frequency of 100. Hz. The frequency of the second
harmonic is ____.
a. 25.0 Hz
b. 50.0 Hz
c. 100. Hz
d. 200. Hz
e. 400. Hz
18. A 40.0-cm long plastic tube is open at both ends and resonating in its first harmonic. The wavelength
of the sound which will produce this resonance is ____.
a. 10.0 cm
b. 20.0 cm
c. 40.0 cm
d. 80.0 cm
e. 160. cm
19. The diagrams below represent four different standing wave patterns in air columns of the same
length. Which of the columns is/are vibrating at its/their fundamental frequency? Include all that apply.
20. The diagrams above represent four different standing wave patterns in air columns of equal length.
Which of the columns will produce the note having the highest pitch?
a. A
b. B
c. C
d. D
21. A 440.-Hz tuning fork is held above the open end of a water-filled pop bottle and resonance is
heard. The length of the pop bottle (bottom to top) is 28.2 cm. If the speed of sound is 345 m/s, then to
what height is the pop bottle filled with water?
LT #4: Define the Doppler shift. Use the Doppler shift equation to determine pitch.
22. Consider the diagram below of several circular waves created at various times and locations. The
diagram illustrates?
a. interference
b. diffraction
c. the Doppler effect.
d. polarization
23. In the diagram for Q22, a person positioned at point A would perceive __________ frequency as the
person positioned at point B.
a. a higher
b. a lower
c. the same
24. A girl moves away from a source of sound at a constant speed. Compared to the frequency of the
sound wave produced by the source, the frequency of the sound wave heard by the girl is ____.
a. lower.
b. higher.
c. the same.
25. An earth-based receiver is detecting electromagnetic waves from a source in outer space. If the
frequency of the waves are observed to be increasing, then the distance between the source and the
earth is probably ____.
a. decreasing.
b. increasing.
c. remaining the same.
26. Use the Doppler equation for a moving source to calculate the observed frequency for a 250 Hz
source of sound if it is moving with a speed of ____ . (Assume that the speed of sound in air is 343 m/s.)
a.
30 m/s towards the observer.
b.
30 m/s away from the observer.
c.
300 m/s towards the observer.
d.
300 m/s away from the observer.
MULTIPLE CHOICE PRACTICE:
Waves and Sound
1. Sound waves in air are transverse waves.
A. True
B. False
Consider the wave shown to the right in Figure 14.1:
2. In Figure 14-1, the wavelength is:
A. 4 m
B. 2 m
C. 1 m
D. cannot be determined from the given information
Figure 14-1
3. In Figure 14-1, the frequency is:
A. 0.5 Hz
B. 1 Hz
C. 2 Hz
D. 4 Hz
4. Sound travels fastest in:
A. gases
B. liquids
C. solids
D. sound travels the same speed regardless of the medium
5. As the temperature of the air increases, what happens to the velocity of sound? (Assume that all other factors
remain constant.)
A. it increases
B. it decreases
C. it stays constant
D. it increases when atmospheric pressure is high, and decreases when the pressure
is low.
6. The pitch of a sound is determined by:
A. the amplitude
B. the speed
C. the wavelength
D. the frequency
7. Sound vibrations with frequencies less than 20 Hz are called
A. infrared
B. supersonic
C. infrasonic
D. ultrasonic
10. A sound source departs from a stationary observer. The frequency heard by the observer is:
A. higher than the source
B. lower than the source
C. the same as that of the source
D. equal to zero
11. Two wave pulses with equal positive amplitudes pass each other on a string, one is traveling toward the right
and the other toward the left. At the point that they occupy the same region of space at the same time:
A. constructive interference occurs
B. destructive interference occurs
C. a standing wave is produced
D. a traveling wave is produced
12. Two wave pulses pass each other on a string. The one traveling toward the right has a positive amplitude,
while the one traveling toward the left has an equal amplitude in the negative direction. At the point that they
occupy the same region of space at the same time:
A. constructive interference occurs
B. destructive interference occurs
C. a standing wave is produced
D. a traveling wave is produced
13. The lowest tone to resonate in a closed pipe of length L is 200 Hz. Which of the following frequencies will not
resonate in that pipe?
A. 200 Hz
B. 400 Hz
C. 600 Hz
D. 1000 Hz
14. Two tuning forks have frequencies of 440 and 522 Hz. What is the beat frequency if both are sounding
simultaneously?
A. 962 Hz
B. 431 Hz
C. 82 Hz
D. 55 Hz