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Re: AT822 Microphone Noise Floor

Subject: Re: AT822 Microphone Noise Floor
From: Dan Dugan <>
Date: Wed, 31 Jul 2002 00:56:26 -0700
>  > Do microphone manufacturers ever already have (or perhaps be willing
>>  to provide as "typical" data) test data for mics at low SPLs?  I
>>  guess what's really important would be frequency response and
>>  sensitivity which would be different than the published numbers at
>>  much higher music and voice levels.

I don't know that the sensitivity or the frequency response are any 
different at low levels for any mike. Of course there's the point 
where the noise mike and/or preamp noise masks the stimulus, but 
otherwise it's a linear function.

>  > I suspect frequency response characteristics under low amplitude is
>>  what leads people to talk about a mic's "reach" of far sounds
>  > relative to near sounds.

I think directivity and sensitivity/noise characteristics are what 
makes the difference.

>It would see to me that other than
>  > directional aspects, a different mic placed into the same
>  > environment, would react simply to the distance squared.

Once you get beyond the distance where proximity has an effect, i.e. 
the curvature of the wavefronts flattens out.

>It seems
>  > the definitive measure would be SNR at an appropriate reference level
>>  somewhere between the near and far sound pressure level.  Perhaps
>>  frequency response further adds to the mystery as "reach" probably is
>>  prone to frequency response affects when we operate near the lower
>>  end of the sensitivity range.

Again, I don't believe that that happens.

-Dan Dugan


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