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Re: Minidisc recorder and noise floor

Subject: Re: Minidisc recorder and noise floor
From: Walter Knapp <>
Date: Wed, 27 Mar 2002 12:01:06 -0500
cgorgen wrote:
>
> I just got into recording of birds and picked up a Sony MZ-R37 off of
> ebay. It was new so I went ahead and bought it. I recieved it this
> week and have tested it out and it works fine. My first problem I
> encountered was the noise floor when using the Audio-technica ATR-55
> microphone. Is there something I can do to remove the noise post
> processing or just get a better mike? I have other microphones and
> they do not seem to create that much noise but they are also not as
> sensitve as the ATR-55.

Obviously getting a mic with a lower noise floor is a option, but it's a
expensive path. And you will find that as you go up that the preamp on
the MZ-R37 has it's own noise floor. So to go better than that you would
be in to both mic and a low noise preamp.

Some of the noise can be filtered out in the computer afterwards. This
is usually done by filtering out selected frequency bands. Note that if
this is done very much, the recording will loose a lot of it's natural
quality, so do a lot of experimentation. And don't depend deeply on
this. There are also noise filters that can be "trained" to the noise
you want removed and actively remove that. Again, overuse will take the
life out of a recording. You should note if recording for scientific
purposes that it's generally considered a no-no to filter. At minimum
verify it's going to be considered ok there.

What you find out in general is that only so much amplification is
possible as amplification increases noise at the same time as what you
want. This is usually the limiting factor of what you can reach with
your setup. Your options to get better reach involve either quieter mics
and pre's, more sensitive mics, or mics that have gain before the
electronics (parabolic mics being the prime ones). Regular directional
or shotgun mics provide a limit on the area they are looking at, but no
gain advantage over non-directional mics. So they may help to cut out
other noise sources out there, they don't help in the balance between
the wanted call and the mic's self noise level. What this all comes out
to in practice is that your cheap way out for less noise is usually a
parabolic. You can get more clean gain for the money that way than in
going to quieter mics. The flip side being that going the route of
shotgun mics you will spend considerable on the quieter mics, and
additional on low noise pres. And, ultimately, even with the quietest,
most expensive shotguns you won't have the reach of a good parabolic.
You should note that you have to be careful buying parabolics. Since
they have this extra gain, some manufacturers skimp on the mics using
mics that are noisier, negating much of the advantage. Noise specs
matter on parabolics too.

The other option is to try and get closer. Then you won't need so much
gain and there will be a larger difference between the dB level of the
call and the noise level of the mic. A lot of the craft of nature
recording is learning how to position yourself for recording. Sometimes
it's not even a matter of getting closer, but moving around to find
where the sound has a clearer path.

In equipment, mics are the important part, where you want to choose
carefully. We really push the limits in nature recording. Which means as
you progress you tie up a fair amount of money in mics. Luckily if cared
for well mics are a long term investment. No matter what the price of
your mics learn good habits of caring for them.

Walt



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