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Re: Normalize samples?
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Re: Normalize samples?


  • Subject: Re: Normalize samples?
  • From: Tim Omernick <email@hidden>
  • Date: Tue, 16 Nov 2004 22:26:05 -0800

I've been getting a lot of off-list replies which state that predicting a microphone's input level is practically impossible. I have an alternate solution to my problem, which I will share for the benefit of everyone on the list who might be attempting the same sort of thing.

Instead of hard-coding a "minimum volume" threshold, I measure the average volume of the ambient noise coming through the microphone over a period of a few seconds. From that average volume, I can then derive a gain value such that when the gain is applied, the signal is at or near zero. Then, I allow any samples with a volume greater than zero to be further processed.

It's sort of like calibrating a scale.  :-)

Thanks,
-Tim Omernick
Engineer, The Omni Group

On Nov 16, 2004, at 6:15 PM, Tim Omernick wrote:

Hi,

I searched through the list archives and could not find an answer to this seemingly simple question. The application I'm working on needs to perform some processing on samples from a microphone, but only if the volume level of those samples exceeds some threshold.

Is there a way to normalize the samples passed to my IOProc so that that every amplitude value lies within the range {-1.0, 1.0}? I get different amplitude ranges for different microphones, even with identical volume settings.

Am I missing something?

Thanks,
-Tim Omernick
Engineer, The Omni Group

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