Doppler Effect When a car with its horn blowing drives by an observer, the pitch of the horn seems higher as it approaches and lower as it recedes (see the ﬁgure below). This phenomenon is called the Doppler Effect. If the sound source is moving at speed relative to the observer and if the speed of sound is, then the perceived frequency is related to the actual frequency as follows.
We choose the minus sign if the source is moving toward the observer and the plus sign if it is moving away. Suppose that a car drives at past a woman standing on the shoulder of a highway, blowing its horn, which has a frequency of 500 Hz. Assume that the speed of sound is . (This is the speed in dry air at .)
What are the frequencies of the sounds that the woman hears as the car approaches her and as it moves away from her?

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Doppler Effect When a car with its horn blowing drives by an observer, the pitch of the horn seems higher as it approaches and lower as it recedes (see the ﬁgure below). This phenomenon is called the Doppler Effect. If the sound source is moving at speed relative to the observer and if the speed of sound is, then the perceived frequency is related to the actual frequency as follows.

We choose the minus sign if the source is moving toward the observer and the plus sign if it is moving away. Suppose that a car drives at past a woman standing on the shoulder of a highway, blowing its horn, which has a frequency of 500 Hz. Assume that the speed of sound is . (This is the speed in dry air at .)

What are the frequencies of the sounds that the woman hears as the car approaches her and as it moves away from her?

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