A whistle you use to call your hunting dog has a frequency...

Name: Problem 53, Chapter 15: College Physics: A Strategic Approach
Uploaded: 2020-11-10T12:56:34-08:00
Duration: 3 min 51 s
Channel: Sheh Lit Chang
Description: A whistle you use to call your hunting dog has a frequency of 21 kHz, but your dog is ignoring it. You suspect the whistle may not be working, but you can’t hear sounds above 20 kHz. To test it, you ask a friend to blow the whistle, then you hop on your bicycle. In which direction should you ride (toward or away from your friend) and at what minimum speed to know if the whistle is working?

A whistle you use to call your hunting dog has a frequency of 21 kHz, but your dog is ignoring it. You suspect the whistle may not be working, but you can’t hear sounds above 20 kHz. To test it, you ask a friend to blow the whistle, then you hop on your bicycle. In which direction should you ride (toward or away from your friend) and at what minimum speed to know if the whistle is working?

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Key Concepts

Doppler Effect

The Doppler effect is the phenomenon in which the observed frequency of a wave changes due to the relative motion between the source and the observer. When the observer and the source move relative to each other, the wave's frequency appears higher when they are moving closer and lower when they are moving apart.

Relative Motion

Relative motion refers to the movement between the observer and the source. The direction and speed of this movement determine how the sound wave is perceived; moving away from a sound source results in a lower observed frequency, while moving toward it results in a higher frequency.

Frequency Shift

A frequency shift occurs because of the Doppler effect; it is the change in the observed frequency compared to the actual emitted frequency. This shift can be calculated using the Doppler formula, allowing us to determine the minimum speed required to bring a sound's frequency into a different range.

Human Auditory Range

The human auditory range is the range of sound frequencies that can be perceived by the human ear. Since human hearing is limited to a specific band of frequencies, the Doppler effect can sometimes shift sounds into or out of this audible range, which has practical implications for testing or perceiving sounds that are normally beyond our hearing.

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