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Re: noise

Subject: Re: noise
From: Dan Dugan <>
Date: Thu, 22 Sep 2005 11:38:28 -0700
Rob Danielson, you wrote,

>Professor Dugan, I signed up for the course  in Audio Measurement
>Reference Levels, again. Charts 3 and 4 here
>http://www.rane.com/note148.html  show mic sensitivity as -dBu and as
>mV/Pa.

One of the problems with mic specs is that people use different
scales and you have to convert to compare. The mV/Pa is typical. dBu
for sensitivity isn't; Shure and Sennheiser reference dB re 1V. Rane
is converting to dBu because they're trying to make it easier for us.

>Seems not to be a simple arithmetic relation/conversion. What
>is the "-32 dB" sensitivity measurement you are working with
>referenced to or need it be?

Any dB figure except gain is ambiguous unless the reference is noted.
dBu is shorthand for 0 =3D .775Vrms. dBV is re 1Vrms. dBm is re 1
milliwatt, a power level, not a voltage level, so it depends on the
impedance. It's gone out of style because we don't impedance-match
audio connections any more.

-Dan Dugan


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