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Re: effect of mic sensitivity

Subject: Re: effect of mic sensitivity
From: "Rob Danielson" danielson_audio
Date: Sun Feb 24, 2008 8:18 pm ((PST))
At 3:55 PM +0000 2/24/08, oryoki2000 wrote:
>I'd appreciate it if someone could help improve my understanding of
>mic sensitivity and its effect on the loudness of a recording.
>
>Let's say the sensitivity of Mic A is rated at 30 mV/Pa, and mic B is
>rated at 15 mV/Pa. I think this means that the voltage Mic A sends to
>the recorder will be twice as high as the voltage Mic B sends when
>exposed to the same reference sound.
>
>Now think of using Mic A and Mic B with the same recorder, using the
>same settings. Will the recording of a reference sound made with Mic
>A appear to the listener to be twice as loud as the recording of the
>same reference sound made with Mic B?
>
>Or, since human hearing responds in a more logarithmic way to
>increases in sound pressure, will the recording made with Mic A appear
>to the listener to be only slightly louder than the recording made
>with Mic B?
>
>Thanks.
>--oryoki
>

One, practical answer is "Mic A will have a substantially more
output."   My MKH-80 has 40 mV/Pa sensitivity and my mkh40 has 25
mV/Pa. I can set my MKH 40 at max gain and match this level with mkh
80 set just before or at the threshold of the +10dB final gain "bump"
on the 744T.

Trouble sets in with low sensitivity. The DAT Heads Mic FAQ used to
suggest something simple like, "...avoid purchasing a mic with less
than 10 mV/Pa."  The Rode NT-4 is rated at 12mV/Pa sensitivity and
the students almost always use full gain on their Hi-MD recorders
(75dB gain) to record ambience in quiet places. With 16dB(A)
self-noise, the NT-4 isn't perfect for the job, but its low
sensitivity usually insures that some Hi-MD pre noise will also be
audible. Rob D.



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