Two identical loudspeakers, placed close to each other inside a room, are supplied with the same sinusoidal voltage. One can imagine a pattern around the loudspeakers with areas of increased and decreased sound intensity alternately located. Which of the following actions will NOT change the locations of these areas?

A

Moving one of the speakers

B

Changing the amplitude of the signal voltage

C

Changing the frequency of the signal voltage

D

Replacing the air in the room with a different gas