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3. Re: sanken cuw-180 recording

Subject: 3. Re: sanken cuw-180 recording
From: "Eric Benjamin" ericbenjamin2
Date: Wed Jun 20, 2012 2:07 am ((PDT))
> The A-law issue is actually more complex than just 'levels'.

I agree with you, it certainly is.  And I particularly agree with the idea =
the use of a weighting curve to create a single number noise level doesn't =
the whole story.

But the most recent work on equal loudness, as embodied in the ISO 226: 200=
shows that A weighting does in fact conform quite well to equal loudness
contours, at least relative to ITU-R BS.468.  The data in the fourth figure=
your link to the Wikipedia article on A-weighting illustrates that.

Going back to the BBC research report EL-17, their emphasis was primarily o=
types of noise other than the random noise produced by microphones.  They w=
attempting to find a noise measurement method that produced ratings equal t=
subjective ratings for impulsive noises, carrier leakage, hum, and other ty=
of noise.  So EL-17 isn't really relevant to the question at hand regarding=
noise of microphones.

So what is relevant to microphone noise measurement?  Noise measurements fo=
microphones had ought to allow us to make useful comparisons between one ty=
pe of
microphone and another.  For instance, if one microphone has a measured sel=
noise that is lower than another, then it had ought to sound quieter.  Does=

A-weighting do that?  Does CCIR weighting?  If we were to order the noise
measurements of microphones, first using A-weighting and then using CCIR
weighting, then which one creates an order that is most like subjective ran=
 I don't have an answer to that, but it turns out that rankings using
A-weighting and CCIR weighting are very close.  If one subtracts the A-weig=
self noise from the CCIR-weighted self noise, the difference is almost alwa=
between 9 and 11 dB.  So both weighting systems are almost equivalent for t=
purpose.  My audio analyzer allows me to easily select either weighting fil=
but I stick with A-weighting because there is very little effective differe=
between the two systems for my purposes.

One method that would be better would be to use a loudness measuring system=
mimics the way human hearing assesses loudness.  One such method is that
proposed by Moore and Glasberg:

Moore, B.C.J., Peters, R.W. & Glasberg, B.R. (1996) "A revision of Zwicker'=
loudness model", Acta Acustica, vol.82, pp.335-345.

These types of models are complicated, but they produce results which are m=
more nearly perceptually correct than do simple weighting networks.  I'll w=
up some numbers if anyone is interested.

Meanwhile, does anyone know of manufacturers who publish both A-weighted an=
d 468
weighted noise specs, other than AKG, Sennheiser, Schoeps, and DPA?

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