Expression Evaluator

GoldWave general discussions and community help
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jdeligiannis
Posts: 34
Joined: Sat Mar 05, 2005 1:50 am

Expression Evaluator

Post by jdeligiannis »

I don't know much about the Expression Evaluator, but by playing around with it, I think I got the concept. Entering certain equations into it will create certain sounds. What I want to know, however, is can this tool evaluate my sound files and give me the mathmatical equation that would reproduce them?

If not, do you think such a feature can be added into the next GoldWave, or perhaps as a plug-in?

Thanks.
DougDbug
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Post by DougDbug »

I'm not sure this is even possible... I guess it depends on how complex your sound is. If it's a simple sine wave, sure you can reproduce it. But if it's regular music (i.e a CD with multiple instruments and maybe a vocal) the most-simplfied mathmatical representation is the WAV/PCM sample-series.

You might look for some FFT software (Fast Fourier Transform)

The Fourier Transfeom converts the information from the time-domain to the frequency domain. This means that you can take a (typically very short) section of sound and break it down into it's frequency components.

If you were to apply one FFT calculation to the entire song, you would loose all of the timing information. The frequency content would match the original, but all of the sounds, notes, harmonics, and overtones would playing at the same time... Just a bunch of noise! :shock:

Goldwave has FFT, but AFAIK it's only used in the background (You can't actually extract the mathematical information). GoldWave uses FFT for pitch-shifting, or to change the tempo/playback speed without changing the pitch....
GoldWave Inc.
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Re: Expression Evaluator

Post by GoldWave Inc. »

A plug-in that evaluates a sound and turns it into a simple equation would be the holy grail of audio compression. Even using a Fourier Transform would result in an equation as big (if not bigger) than the entire sound file. A lot of the terms can be discarded (which is sort of how MP3 compression works), but unless you are working with very simple sounds, that kind of evaluation is not really practical or useful.

Chris
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