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One singer produces an intensity of 10−4 Watts/m2 when she sings a distance of 3 m from a listener.

If you get 10 singers together who sing at the same volume at the same distance, what will be the intensity the listener hears?

  1. 10−3 Watts/m2
  2. 10 + 10−4 Watt/m2
  3. 1.1 × 10−4 Watts/m2
  4. 10−5 Watts/m2

Question 17.1

2 of 10

One singer produces a intensity level of 80 dB when she sings a distance of 3 m from a listener. If you get 10 singers together who sing at the same volume at the same distance, what will be the intensity level the listener hears?

  1. 81 dB
  2. 90 dB
  3. 100 dB
  4. 800 dB

Question 17.2

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Consider a pipe of length L that is open at one end and closed at the other end.

What are the wavelengths of the three lowest-pitch tones produced by resonance in this pipe?

A) 4L, 2L, L

B) 2L, L, L/2

C) 2L, L, 2 L/3

D) 4L, 4L/3, 4L/5

Question 17.3

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A singer sings a note: “LAAAA”.

The singer repeats the same note, but louder.

What has increased about the sound wave when it is louder?

  1. The amplitude
  2. The frequency
  3. The speed
  4. All of the above
  5. 2 out of 3 of A, B and C

Question 17.4

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A singer sings a note: “LAAAA”.

The singer sings again with the same loudness, but a higher pitch (for example a B instead of an A).

What has increased about the sound wave when it is a higher pitch?

  1. The amplitude
  2. The frequency
  3. The speed
  4. All of the above
  5. 2 out of 3 of A, B and C

Question 17.5

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An observer is standing in the middle of the road, as a police car approaches her at a constant speed, vs. The siren on the police car emits a “source frequency” of fs.

Question 17.6: Which statement is true?

  1. The frequency she observes rises steadily as the police car gets closer and closer.
  2. The frequency she observes steadily decreases as the police car gets closer and closer.
  3. The frequency she observes does not change as the police car gets closer.

7 of 10

An observer is standing in the middle of the road, as a police car approaches her at a constant speed, vs. The siren on the police car emits a “source frequency” of fs.

Question 17.7: Which statement is true?

  1. The steady frequency she observes is higher than fs.
  2. The steady frequency she observes is lower than fs.
  3. The steady frequency she observes is equal to fs.

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Question 17.8

  • What is the pitch of the sound shown? [The horizontal axis stretches from 0 to 0.035 seconds.]
  • 0.01 Hz
  • 10 Hz
  • 50 Hz
  • 100 Hz
  • 1000 Hz

Pressure versus Time Graph

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Question 17.9

  • What is the pitch of the sound shown? [The horizontal axis stretches from 0 to 2500 Hertz.]
  • 0 Hz
  • 130 Hz
  • 650 Hz
  • 1970 Hz
  • 2500 Hz
  • The LOWEST frequency is the “pitch” you hear (assuming all the higher frequencies are integer-multiples of this lowest frequency).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fourier Spectrum

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Question 17.10

  • On a real guitar string which you pluck, which mode shape do you get?
  • n = 1
  • n = 2
  • n = 3 or higher
  • Many modes can be combined at once on a single string.