Vicki,
An interesting question. In the case of microphone sensitivity, there have
been two reference levels in use over the years. One of them is output level
relative to 1 uBar, and the other one is output level relative to 1 Pa. But
people usually think of sound level in terms of dB SPL. 1 Pa is 94 dB SPL and
1 uBar is 74 dB SPL. The voltage level on the output is either stated in dBu
(or m), which is dB relative 10 .775 Volts, or in dBV, which is dB relative to
1 Volt. So the acoustic levels are 20 dB apart and the voltage levels are 2.26
dB apart. Are we confused yet? A little arithmetic is necessary.
The EM172 I know about. Its sensitivity is -28 dBV/Pa, meaning that it puts
out -28 dBV when a sound level of 94 dB SPL is present. -28 dBV is the same as
38 mV, as Rob wrote. The self noise is 14 dBA. This is a very sensitive
microphone capsule and also a very quiet one.
The sensitivity spec for the Olympus microphone was probably -68 dBu/uBar,
because that was the way that many manufacturers did it in 1988. One dBu =
-2.26 dBV, and 1 uBar = -20 dB/Pa. So the sensitivity of the Olympus me9 is
probably -50 dBV/Pa. A very low sensitivity by more modern standards. There has
been a lot of improvement in microphone performance over the last quarter
century.
As for frequency response, a typical EM172 is fairly flat from 20 Hz to 20 kHz,
with about a 4 dB lift at 6 kHz and then down 3 dB at 20 kHz. It's really,
really good for the price.
On Thursday, November 20, 2014 4:14 PM, "vickipowys
[naturerecordists]" <> wrote:
Back in 1988 I bought a brand new Sony Pro Walkman WM-D6C, a cassette
recorder that many field recordists were using at the time.
I also purchased two Olympus Pearlcorder ME9 microphones (omni,
tieclip), and had them wired as a stereo pair, and went off happily
recording sounds all around Australia.
I would like to get a rough idea of the sound quality of the ME9 mics,
compared to the newer Primo EM172 (omni electret) mics that are used
today, by me and many others.
All I have to go on are the ME9 specifications:
Frequency response: 50-13,000Hz
Mike sensitivity: -68dB
(the mics were powered by small mercury batteries).
How can I compare the ME9 specifications with the EM172 mics:
Frequency response: 100-12,000Hz fairly flat, but also may go lower,
and higher up to 20,000 with some drop off.
Mic sensitivity: 14 dB(A) / 38 mV/Pa (as shown on a chart by Rob
Danielson)
i.e. can someone please tell me what -68dB is as millivolts per pascal
(mV/Pa)? Or offer other comments?
Many thanks!
Vicki Powys
Australia
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