Question

What occurs when the pitch increases and the sound source is in motion? Explain your answer.

Answer 1

The pitch of a sound is related to the frequency of the sound wave...higher pitch = greater frequency. If a sound source is moving towards you, the wavelength is shortened. If the sound source is moving away from you, the wavelength is lengthened. Since the speed of sound (for any given conditions) is constant, the universal wave equation tells you what happens to the perceived frequency of sound emitted from a moving source:
\[v=f \lambda \]Make any sense?

Answer 2

since v is constant, and v = f*lambda
when lambda (wavelength) becomes smaller, which happens as a moving sound waveform approaches it gets compressed, frequency must go up to balance it. Thus pitch goes up.

conversely when lambda becomes greater, which happens as the sound source moves away it stretches the wavelength of the waveform, frequency gets smaller to balance this. Thus pitch goes down.