Question 1

Which of the following best describes the difference between a sound wave and a light wave?

Accepted Answer

Sound waves are longitudinal and require a medium, while light waves are transverse and can travel through a vacuum.

Question 2

The speed of sound in an ideal gas is given by which of the following equations?

Accepted Answer

$$v = \sqrt{\frac{\gamma RT}{M}}$$

Question 3

A sound wave in air at 20°C has a speed of approximately 343 m/s. If the temperature increases, what happens to the speed of sound?

Accepted Answer

The speed of sound increases because the average kinetic energy of air molecules increases.

Question 4

Which of the following is the correct formula for the intensity $$I of a $$sinusoidal sound wave in a fluid?

Accepted Answer

$$I = \frac{P_{max}^2}{2 \rho v}$$

Question 5

A sound wave has a pressure amplitude of $$P_{max}. If $$the pressure amplitude is doubled, what happens to the intensity of the sound wave?

Accepted Answer

The intensity increases by a factor of 4.

Question 6

The decibel scale for sound intensity level $$\beta is $$defined as:

Accepted Answer

$$\beta = (10\ \mathrm{dB}) \log_{10} \left( \frac{I}{I_0$} \right)$$

Question 7

Two sound sources emit waves of frequencies 440 Hz and 444 Hz. What is the beat frequency heard by an observer?

Accepted Answer

4 Hz

Question 8

A flute (open at both ends) and a clarinet (closed at one end) are the same length. Which instrument produces the lower fundamental frequency and why?

Accepted Answer

The clarinet, because the fundamental wavelength is four times the pipe length.

Question 9

A stationary observer hears a higher frequency as an ambulance approaches and a lower frequency as it moves away. This phenomenon is best explained by:

Accepted Answer

The Doppler effect

Question 10

A pipe closed at one end has a length $$L. $$What is the frequency of its third harmonic?

Accepted Answer

$$f_3$$ = \frac{3v}{4L}$$

Question 11

A sound wave travels from air into water. Which of the following statements is correct?

Accepted Answer

The speed of sound increases and the wavelength increases.

Question 12

If the intensity of a sound increases from $$1.0 	imes 10$$^{-6}$$\ \mathrm{W/m^2$} to$$ $$1.0 	imes 10$$^{-4}$$\ \mathrm{W/m^2$}$$, by how many decibels does the sound intensity level increase?

Accepted Answer

20 dB

Question 13

A bat uses echolocation to detect an insect 5.0 m away. If the speed of sound in air is 340 m/s, how long does it take for the echo to return to the bat?

Accepted Answer

0.029 s

Question 14

Which of the following best explains why you can hear low-frequency sounds from a party through a closed door, but not high-frequency sounds?

Accepted Answer

Low-frequency sounds diffract more easily around obstacles.

Question 15

A supersonic jet travels at Mach 2. If the speed of sound is 340 m/s, what is the speed of the jet?

Accepted Answer

680 m/s

Question 16

Which of the following is the condition for constructive interference between two sound waves from coherent sources?

Accepted Answer

$$\Delta r = m \lambda$$, where $$m is an $$integer

Question 17

A violin string is tuned using a 440 Hz tuning fork. If 3 beats per second are heard, what are the possible frequencies of the violin string?

Accepted Answer

437 Hz or 443 Hz

Question 18

Which of the following is true about the human ear's sensitivity to sound?

Accepted Answer

It is most sensitive to frequencies around 1000 Hz.

Question 19

Active noise cancellation works best for which type of sound?

Accepted Answer

Low-frequency, continuous sounds

Question 20

A standing wave in a pipe closed at one end and open at the other has a length $$L = 0.5 m. $$What is the fundamental frequency if the speed of sound is 340 m/s?

Accepted Answer

170 Hz

Chapter 16: Sound and Hearing – Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard