Sorry folks I've just posted on this subject but I need to cooment on
this quote which has just downloaded:
> SPL limit >=3D 140dB
> S/N =3D> 80dB +/- 10 (higher is better)
> Self Noise <=3D 15dB +/- 10 (A weighted / lower is better)
> Response =3D 20Hz-20kHz
What on earth is being recorded at 140dBA? What mic input stage will
handdle that? That's well into ear damage country. 90 dBs is very
uncomfortable, 50 dB higher is 100,000 times that sound energy level.
Your ear wax will be moving. (Not a recommended treatment)
A S/N is relevant to a recording, not a transducer. With a background
noise of 30dBs (quiet), That's a recording of a 110 dBA sound. For a
loud natural sound at 90dBA, this is asking for a noise level of
Message: 10DbA.
Subject: That simply can't be done technically with the very best pro
gear.
A-weighting doesn't help noise figures as the thermal Johnson noise of
the air rises with frequency. That's the datum for self noise. BTW I
heard it once as a young teenager in a windless grassland and after my
ears had settled down for over an hour. My heartbeat was loud and I
could hear my pulse and behind that was a very high hiss.
Beware of frequency response figures that don't quote +/- limits.
Beware of those which do, as the curves are frequently smoothed out.
As I said in my last email, above all, trust your ears first.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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