Question

As a sound source approaches someone, the frequency of the sound wave

increases.
decreases.
decreases, then increases.
remains constant.

A? D? Idk someone please help thank you!

Answer 1

If the sound source is approaching you, the frequency you hear is higher than the real frequency of by the sound. How much higher depends on how fast the source is approaching. If the source's speed is constant, then the frequency you hear is constant ... higher, but not increasing.