# Ratio of Size to Pitch and Time

Just for interest sake...

In animation, if you want to realistically film a model of a certain scale, you use a faster frame rate. There is a formula for that, which I don't know.

I'm wondering if there is such a formula in sound? If let say we record the sound of a model tree falling (at a scaling of 1/50th), would there be a ratio of pitch and time manipulation of some sort?

Or forgetting about models, is there logic behind making a sound sound X-times bigger?

It's complicated.

One can see picture relates to physics in a linear fashion: it's all about distances. Take a tennis ball falling VS. the ball in Snake Eyes (a big metal ball sitting on top of a building). If you drop both of these from a 1000ft above the ground, they'll hit the ground precisely at the same time (considering air friction is negligible), however one - the metal ball - is significantly heavier than the other. Mass does not impact the speed of things, but size does.

For a visual effect, you'll drop a - chromed - tennis ball free falling from a 10ft height. In the movie, it's supposed to be a metal ball falling from 1000ft high. In reality, it'd take the metal ball 7.89s to touch the ground. However your tennis ball will drop 10ft in 0.789s. You'd need to slow your footage down 10 times, or in other words shoot at a 10 times higher frame rate for the visual effect to work.

In sound, you can't always be as mathematical as with picture simply because it's so much more complex. One must considerate the time domain and the frequency domain/spectrum seperately.

On the one hand, I think it was Murch's trick to speed up a sound 4 times, worldize it and speed the worldized version down 4 times. That'll give you the reverb of the room you worldized in, only 4 times bigger. Just like picture, that's merely making a scale model and slow it down, playing with the apparent distances the sound waves would travel.

On the other hand, in my experience, a car twice as big as another one doesn't sound like it 1 or 2 octaves down. They both have their own sound within the full spectrum.

I believe that apparent size says it all: if it's close enough to look big to you, then you might want to give it more detail, however if you see it small, then you're not close enough to hear much details.

I hope what I wrote is understandable...

• Wow, quite the answer there. Makes a lot of sense though. Thanks so much :-) Sep 20, 2010 at 21:05