Question 1

The Doppler shift explains

Accepted Answer

The Doppler shift describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. It explains why the pitch of a siren on a moving vehicle, such as a police car, appears higher as it approaches an observer and lower as it moves away. This is because the sound waves are compressed as the source approaches and stretched as it moves away, changing the perceived pitch.

Question 2

If a jet plane were to double its MACH-speed, its half-angle will

Accepted Answer

The half-angle of a shock wave is inversely related to the Mach number. If the Mach number doubles, the half-angle decreases.

Question 3

A trombone or a trumpet can be considered a(n)

Accepted Answer

A trombone or a trumpet can be considered an open organ pipe because both ends of these instruments are open to the air, allowing air to move in and out freely, similar to the way air resonates in an open organ pipe.

Question 4

Only odd harmonics can be produced in a(n) ________ organ pipe.

Accepted Answer

In a closed organ pipe, only odd harmonics are produced because the boundary conditions allow for standing waves that have a node at the closed end and an antinode at the open end. This results in the fundamental frequency being the first harmonic, and only odd multiples of this fundamental frequency (3rd, 5th, etc.) can exist due to the constraints on the wave patterns within the pipe.

Question 5

After seeing a flash of lightning, if one counts the seconds before hearing the thunder, one can estimate the distance to the flash. How many seconds delay
(a) per mile?
(b) per kilometer?

Accepted Answer

The answer of After seeing a flash of lightning, if...

Question 6

Sound traveling in air at 23.° C enters a cold front where the air temperature is 2.° C. If the sound frequency is 1500. Hz, determine the speed in the warmer air and in the colder air.

Accepted Answer

The answer of Sound traveling in air at 23.° C...

Question 7

What is the ratio of the speed of sound in air at 0° C to the speed at 100° C?

Accepted Answer

The answer of What is the ratio of the speed...

Question 8

On a day when the speed of sound in air is 340. m/s, a bat emits a shriek whose echo reaches it 25.0 ms later. How far away was the object that reflected back the sound?

Accepted Answer

The answer of On a day when the speed of...

Question 9

What is the ratio of the power levels of two sounds with intensity levels of 40. dB and 70. dB?

Accepted Answer

The answer of What is the ratio of the power...

Question 10

What is the intensity of a 70. dB sound?

Accepted Answer

The answer of What is the intensity of a 70....

Question 11

The intensity at a distance of 6.0 m from a source is 6 × 10^-10 W/m². (a) What is the power level emitted by the source? (b) What is the intensity level in dB?

Accepted Answer

The answer of The intensity at a distance of 6.0...

Question 12

Consider a sound intensity of 16. × 10^-8 W/m². (a) What is the sound intensity level? (b) At twice the distance from the source, what would be the intensity level? (c) At how many times the original distance would the intensity level decrease by 12. db?

Accepted Answer

The answer of Consider a sound intensity of 16. ×...

Question 13

One cat meowing produces a sound intensity level of 55. db.
(a) What would be the sound intensity level of 2 cats meowing?
(b) ... of 10 cats meowing?
(c) ... of 100 cats meowing?

Accepted Answer

The answer of One cat meowing produces a sound intensity...

Question 14

Two adjacent sources each emit a frequency of 800. Hz in air where the velocity of sound is 340. m/s. How much farther back would the first source have to be moved so an observer in front of the sources would hear no sound?

Accepted Answer

The answer of Two adjacent sources each emit a frequency...

Question 15

What is the beat frequency of two sounds that have equal amplitudes and frequencies of 440. Hz and 444. Hz?

Accepted Answer

The answer of What is the beat frequency of two...

Question 16

Given 4 tuning forks of frequency 446, 440, 443, and 449 Hz, how many different beat frequencies could be produced and what are they?

Accepted Answer

The answer of Given 4 tuning forks of frequency 446,...

Question 17

James is listening to the same tone coming from two speakers, one 3.49 m away and the other 3.10 m distant. At his position the two tones destructively interfere.
(a) What is the largest possible wavelength of the tone?
(b) If the air temperature is 30.° C, what is the lowest possible frequency?

Accepted Answer

The answer of James is listening to the same tone...

Question 18

Estimate by what percent the perceived frequency of speech changes due to a talking person walking away from another person at rest at a speed of 3 m/s.

Accepted Answer

The answer of Estimate by what percent the perceived frequency...

Question 19

A train moving 30. m/s approaches a station and sounds its whistle and passengers standing at the station hear a pitch of 440. cycles/second. What pitch will be heard when the train is at rest at the station? (assume the air temperature is 20.°C)

Accepted Answer

The answer of A train moving 30. m/s approaches a...

Question 20

"Warp one" (the speed of light) is what Mach number at 20.° C?

Accepted Answer

The answer of "Warp one" (the speed of light) is...

Quiz 14: Sound