Physics Ch. 12

Match the sound intensity on the right with the sound intensity level on the left.

10-12 1 10-11

By what factor would the intensity of a sound wave increase if its amplitude doubled?

4

How much higher is the frequency of each note in the chromatic scale than the previous note?

5.95%

By what factor would the intensity of a sound wave increase if its amplitude tripled?

9

What is the name for the decrease in intensity of a wave as it propagates?

Attenuation

True or false: Some animals use ultrasound (20 to 200 kHz) for echolocation.

True

Most home stereo systems have both bass and treble tone controls, and it is common to see that both are set so that the low and high frequencies in musical material are boosted in volume. This occurs because the human auditory system does not have a(n)________________response to sound across the audible range of frequencies.

equal

What units must the temperature be in to use the equation v = v0√TT0?

Kelvin

A pipe open at both ends of length L resonates in its second harmonic (n = 2). What is the wavelength of the standing wave in the pipe?

L

Consider two thin pipes each closed at one end with the same sound wave speed but different lengths. Is the fundamental frequency of the longer pipe greater than, equal to, or less than the fundamental frequency of the shorter pipe?

Less than

Consider two thin pipes open at both ends with the same sound wave speed but different lengths. Is the fundamental frequency of the longer pipe greater than, equal to, or less than the fundamental frequency of the shorter pipe?

Less than

Select all of the following through which sound waves can propagate.

Liquids Solids Gases

To what is pitch approximately directly proportional?

Logarithmic function of frequency

Rank the following situations according to the frequency heard by the car driver, with the largest frequency at the top and the smallest at the bottom. Assume that the frequency produced by the ambulance is constant, the sound wave propagates through air, and the air is not moving with respect to the ground.

20 30 10 20 20 10 20 30

A hiker on a mountaintop estimates the distance to a river along the valley floor by using her wristwatch to time the arrival of the sound from cars that occasionally appear in a gap in the trees along the road that runs by the river. She measures an average time of 6 seconds. Approximately how far away is the river?

2000 meters

A pipe open at both ends of length L resonates in its fundamental mode (n = 1). What is the wavelength of the standing wave in the pipe?

2L

Rank the following thin pipes open at both ends in terms of their fundamental frequencies, with the largest fundamental frequency at the top and the smallest at the bottom.

340 40 330 40 340 80 330 80

Two birds move away from each other. Their speeds with respect to the air are equal. One bird calls the other with a note of frequency 550 Hz. The other bird hears the note with a frequency of 450 Hz. The speed of sound in the air is 350 m/s. How fast is each bird moving with respect to the air?

35

Rank the following thin pipes each closed at one end in terms of their fundamental frequencies, with the largest fundamental frequency at the top and the smallest at the bottom.

350 30 340 30 350 60 340 60

Rank the following situations according to the frequency heard by the observer, with the largest frequency at the top and the smallest at the bottom. Assume that the frequency produced at the source is constant and that the source is stationary in all cases.

60 10 30 50

A pipe open at both ends of length L resonates in one of its modes. Rank the following according to the wavelength of the standing wave, with the largest wavelength at the top and the smallest at the bottom.

6d 1 5d 2 d 1 d 2

Rank the following thin solid rods in terms of the speed at which sound waves would travel along their lengths, with the largest speed at the top and the smallest at the bottom. Assume that all of the rods have the same Young's modulus.

75 15 50 25

For sounds waves, what is the phase relationship between the graphs of pressure versus position and displacement versus position?

90 degrees out of phase

A string is surrounded by air. Which statement is true?

A transverse wave on the string can cause a sound wave in the air.

Select all of the following that allow humans to determine the location of the source of low-frequency sound waves.

Phase difference Difference in arrival time

Select all of the following that allow humans to determine the location of the source of high-frequency sound waves.

Shape of the pinna Difference in intensity sensed by each ear

Which of the following instruments are able to produce the lowest notes, assuming they are similar lengths?

Bass clarinet (open at one end only) Clarinet (open at one end only)

Rank the following species according to the highest frequency sound waves they can hear, with the largest frequency at the top and the smallest at the bottom.

Bats Dogs Younger humans Older humans

By what factor would the density of a fluid need to change to double the speed of sound waves propagating through it?

Decrease by a factor of 4

As a sound wave propagates through air, properties of the air change depending on position. Select all of the following properties that change because of the sound wave propagation.

Density Pressure

Select all of the following that can cause sound wave attenuation.

Diffraction Absorption

Which of the following instruments are able to produce all integer multiples of the fundamental?

Flute Organ Pipe

On which quantities does the perceived loudness of a sound depend?

Frequency Intensity

Consider two thin pipes open at both ends with the same length but different sound wave speeds. Is the fundamental frequency of the pipe with the larger sound wave speed greater than, equal to, or less than the fundamental frequency of the pipe with the smaller sound wave speed?

Greater than

Select all of the following statements that are true.

In three dimensions, shock waves are cone-shaped. Shock waves are formed when the speed of the source with respect to the medium is greater than the speed of propagation of the wave.

If the sound intensity quadruples, then what happens to the sound intensity level?

It increases by 6 dB.

Rank the following media in terms of the speed of a sound wave propagating through them, with the largest wave speed at the top and the smallest at the bottom.

Steel railroad tracks Pacific ocean Earths atmosphere

Select all of the following temperature changes that would result in the speed of sound doubling in an ideal gas.

TO = 100 K, T = 400 K TO = 200 K, T = 800 K

Select all of the following that are examples of the Doppler effect.

The rise and fall in pitch of a vibrating tuning fork being twirled around above an instructor's head during a class demonstration The rise in pitch of an approaching train whistle

What causes a sonic boom?

The shock wave formed by wave crests piling up on each other.

What is the propagation speed of a wave in a fluid proportional to?

The square root of the bulk modulus The inverse square root of the density

What causes the beat frequency that is produced when two notes are different?

The two waves switching between being in and out of phase.

Two sound waves are played during the same 15 second time interval and are identical except their frequencies are 440 Hz and 442 Hz. Which statement is correct?

They are sometimes 180 degrees out of phase.

Two sound waves are played during the same 10 second time interval and are identical except their frequencies are 510 Hz and 511 Hz. Which statement is correct?

They are sometimes in phase.

Which of the following are ways that animals use sound to locate objects and prey?

They use the time delay between the sound being produced and the return of the echo to estimate distance. They use the Doppler shift of the frequency to determine the prey's velocity.

Rank the following frequency ranges for humans, with the largest frequencies at the top and the smallest at the bottom.

Ultrasound Audible Infrasound

In which medium does sound travel faster?

Water

Select all of the following that vary as a result of the Doppler effect. Assume that a sound wave propagates from the source to the observer.

Wavelength Frequency

A guitarist is using beats to tune. She sounds two strings fingered so that they are playing the same note. When are the strings closer to producing the same note or frequency?

When the beat frequency gets smaller

Which of the following statements is correct?

When the source moves toward the observer, the observer measures a larger frequency.

A thin pipe open at both ends of length L and sound wave speed v resonates in its fourth harmonic (n = 4). What is the resonant frequency of the standing sound wave in the pipe?

f = 2v/L

A thin pipe closed at one end of length L and sound wave speed v resonates in its third harmonic (n = 3). What is the resonant frequency of the standing sound wave in the pipe?

f = 3v/4L

A thin pipe open at both ends of length L and sound wave speed v resonates in its second harmonic (n = 2). What is the resonant frequency of the standing sound wave in the pipe?

f = v/L

Since air is generally cooler in the winter than in the summer, the difference in time between a flash of lightning and a clap of thunder is________________in the winter than it is in the summer.

more

How do sound waves propagate through air?

The air molecules oscillate (move back and forth) parallel to the direction of propagation.

What is meant by the timbre of an instrument?

The combination of relative intensities of the harmonics for a given note.

Consider the spectral data for a trumpet and a trombone both playing an A4 (440 Hz) tone. Why do these instruments, though playing the same note, sound different?

The higher order harmonics are different for each instrument.

If the speed of sound in a medium is inversely proportional to the square root of the density of that medium, why do sound waves usually travel faster in liquids than in gases?

The liquids are less compressible.

Select all of the following statements that are true regarding beats.

The loudness of the superposition of the two waves increases and decreases periodically. The beat frequency is directly proportional to the difference of the frequencies of the two waves. The intensity of the superposition of the two waves increases and decreases periodically. The amplitude of the superposition of the two waves increases and decreases periodically.

Rank the following sounds according to their sound intensity, with the largest sound intensity at the top and the smallest at the bottom.

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