Question 1

If the intensity of a sound under water at a distance of 3 m from the source is 4.5 × 10^-2 W/m², what is the intensity when you move to a position 10 m from the source?

Accepted Answer

The answer of If the intensity of a sound under...

Question 2

Humans hear due only to vibration of the eardrum.

Accepted Answer

Humans hear sounds not only through the vibration of the eardrum but also through the transmission of these vibrations via the ossicles to the cochlea in the inner ear, where they are converted into nerve impulses that the brain interprets as sound.

Question 3

If an object is vibrating, and another object acts on it with an external vibration close to the original frequency, the result is a dramatic increase in amplitude.

Accepted Answer

This phenomenon is known as resonance, where an external vibration matching the natural frequency of an object can cause the object to vibrate with a significantly increased amplitude.

Question 4

A sound wave is a wave that propagates through a medium: the more elastic the medium, the bigger the resistance to the sound and therefore the slower the speed of the sound.

Accepted Answer

The speed of sound is actually faster in more elastic mediums because elasticity facilitates the transmission of sound waves more efficiently than resistance does.

Question 5

A clarinet and a flute have nearly cylindrical bores with similar length and diameter, yet they are quite different in tone quality and range of pitch. Discuss those differences and explain the reasons.

Accepted Answer

The answer of A clarinet and a flute have nearly...

Question 6

A dolphin emits an ultrasound pulse, which bounces off a small fish about 50 m away. How much time is required for the dolphin to notice the fish? The density of seawater is 1028 kg/m³, and the bulk modulus of water is 2.34 × 10⁹ Pa.

Accepted Answer

The answer of A dolphin emits an ultrasound pulse, which...

Question 7

For sound to be heard by the human ear, the displacement of air by the sound wave has to be significant, at least a few centimetres.

Accepted Answer

Sound can be heard even with very small displacements of air; human ears are sensitive to displacements much smaller than a centimetre, down to nanometre scales.

Question 8

In music, a one octave interval corresponds to a factor of 2 in frequency. How will the sound of a wind instrument change if you alter it (for example, by sliding a pipe, or closing holes) in such a way that the tube gets longer by a factor of 4? The speed of sound in air is 343 m/s.

Accepted Answer

The answer of In music, a one octave interval corresponds...

Question 9

What is the fifth harmonic frequency of a 3.4 m organ pipe open at one end and closed at the other end? The speed of sound in air is 343 m/s.

Accepted Answer

The answer of What is the fifth harmonic frequency of...

Question 10

The speed of sound depends only on the density of the medium that it travels through.

Accepted Answer

The speed of sound is affected by several factors including the density of the medium, the medium's elasticity, and the temperature of the medium.

Question 11

A sound wave is a longitudinal wave.

Accepted Answer

In a sound wave, the particles of the medium vibrate back and forth in the same direction as the wave travels, which is characteristic of longitudinal waves.

Question 12

If one sound is 70 dB and another sound is 100 dB, the difference in intensity between the two sounds is 1000 times.

Accepted Answer

The decibel scale is logarithmic, meaning each 10 dB increase represents a tenfold increase in intensity. A 30 dB difference (100 dB - 70 dB) corresponds to a 10^3 or 1000 times increase in intensity.

Question 13

What fraction of atmospheric pressure (P_atm = 1.0 × 10⁵ Pa) is produced by a sound wave of frequency 1600 Hz and displacement amplitude D = 1.8 × 10^-11 m? The speed of sound in the air is 343 m/s, and the density of air is 1.2 kg/m³ at 20°C.

Accepted Answer

The answer of What fraction of atmospheric pressure (P_atm =...

Question 14

A louder sound moves faster through air than a sound that is less loud.

Accepted Answer

The speed of sound through air is determined by the temperature and composition of the air, not by the loudness (amplitude) of the sound.

Question 15

Figure 15.4  The figure shows an overview of a cochlea.
-In Fig. 15.4, what is the order of frequencies exciting the membrane from the oval window on the left toward the right in the basilar membrane?

Accepted Answer

The answer of Figure 15.4  The figure shows an...

Question 16

The 100 dB sounds of 40 Hz and 3 kHz are equally loud, because the loudness expressed in decibels is the same.

Accepted Answer

The perceived loudness of a sound not only depends on its intensity (decibels) but also on its frequency. Human hearing sensitivity varies with frequency, and sounds at 40 Hz and 3 kHz do not have the same perceived loudness even if their sound pressure levels are the same in decibels.

Question 17

In music, a 1 octave interval corresponds to a factor of 2 in frequency. The lowest C on a piano, C1, has a frequency of 32.7 Hz, and the highest C, C8, is 7 octaves higher. What is the ratio of lengths of organ tubes that would produce C1 and C8 frequencies? The speed of sound in air is 343 m/s.

Accepted Answer

The answer of In music, a 1 octave interval corresponds...

Question 18

If the amplitude of a sound wave is 0.001 atm, what is the maximum net force it produces on an eardrum that has an area of about 1 cm²? Is this a loud or a soft sound?

Accepted Answer

The answer of If the amplitude of a sound wave...

Question 19

Calculate the speed of sound for a winter temperature of -30°C. Is it slower or faster than the speed of sound at +30°C?

Accepted Answer

The answer of Calculate the speed of sound for a...

Question 20

You compress an ideal isothermal gas in a horizontal container with a piston. When you release the piston, the system restores directly to the state of equilibrium.

Accepted Answer

The answer of You compress an ideal isothermal gas in...

Quiz 15: Sound

If the intensity of a sound under water at a distance of 3 m from the source is 4.5 × 10-2 W/m2, what is the intensity when you move to a position 10 m from the source?