Question

Trumpeter A holds a B-flat note on the trumpet for a long time. Person C is running towards the trumpeter at a constant velocity. Person B is running away from the trumpeter at the same rate. Person D is standing still the whole time.
Which person hears a note that is higher than the B-flat?
A) Person A
B) Person B
C) Person C
D) Person D

Answer 1

Answer: the answer is c

Explanation:

 

Person C hears a note that is higher than a B-flat. This is because as the runner approaches the stationary trumpeter, the sound waves become compressed. This reduces the wavelength and increases the frequency.

(usa testprep explanation)

Answer 2

You didn't mention it, but the trumpeter herself has to be standing still.

Person C, the one running towards the trumpeter, hears a pitch
that is higher than B-flat.  (A)

Person B, the one running away from the trumpeter, hears a pitch
that is lower than B-flat.

Person D, the one standing still the whole time, hears the B-flat.