How Does Quadrupling Playback Speed Affect the Mach Number in Film Effects?

[Idioticsmartie]

Speed of Sound and Mach

Homework Statement

You are hired as the physics consultant for a large movie studio. The producer is way over budget and wants to perform some special effects that will save him money. He decides to shoot the dramatic action boat chase scene with the boats going at 1/4 the speed of what will be seen on film. He quadruples the speed of playback. Explain why or why not this will work.

Homework Equations

Mach # = velocity of boat/ speed of sound
Speed of sound = 331 + 0.60*T
T = temperature

The Attempt at a Solution

I don't even know where to begin. I don't think it will work, but maybe if someone could point me in the right direction?

 

[learningphysics]

I think the idea is that the sound won't be right. What happens to the frequency of the sounds heard when playback is quadrupled?