Increase in the volume of a sound

[EchoTheCat]

Homework Statement

A person turns up the volume on a radio. Which aspects of the motion of a point on the diaphragm must increase?
a. maximum displacement only
b. average speed only
c. both maximum displacement and average speed
d. neither maximum displacement nor average speed

Homework Equations

speed = wavelength * frequency

The Attempt at a Solution

I thought it would be (a), because in order for the sound to get louder, the amplitude must increase, but amplitude doesn't affect speed. so the answer is (c) and I'm not sure why.

 

[Matthew Bay]

I could be wrong, but the average speed of the diaphragm must increase in order to maintain the same frequency. If you increase the amplitude, the point will be traveling farther. If it traveled farther at the same average speed, it would take longer to cycle. An increase in the period would decrease the frequency and you would get distortion. Thus you need to increase the average speed of the diaphragm as well as the displacement.

 

[berkeman]

I could be wrong, but the average speed of the diaphragm must increase in order to maintain the same frequency. If you increase the amplitude, the point will be traveling farther. If it traveled farther at the same average speed, it would take longer to cycle. An increase in the period would decrease the frequency and you would get distortion. Thus you need to increase the average speed of the diaphragm as well as the displacement.

Looks correct to me.