To find:
What will change when the observer moves relative to the source?
Step-by-step explanation:
The change in the frequency of a wave emitted by a source is called the doppler effect.
The Doppler effect can be described as the difference between the frequency emitted by a source and the frequency observed by an observer who is in a relative motion with the source.
Final answer:
Thus, as you move past the source, the pitch (frequency) of the sound will change.
Therefore the correct answer is option B.