Question

if a source of sound waves is rapidly approaching a person the sound heard by the person appears to have

Answer 1

If a source of sound is approaching a person, no matter
how fast or slow, then the sound heard by the observer
appears to have higher frequency (shorter wavelength)
than the sound actually generated by the source has.

Answer 2

Answer

Increasing frequency

Explanation

When the source of sound and the observer are moving towards each other the frequency tends to be increasing. Since wavelength is inversely proportional to the frequency, the wave decreases when the frequency increases.

These effect is called the Doppler effect named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842