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Re: Mic Terminology

Subject: Re: Mic Terminology
From: Walter Knapp <>
Date: Sat, 19 Feb 2005 11:29:42 -0500
From: Rob Danielson <>

> Sorry I'm not making myself clear. The relation I hoped to describe
> with the phrase "noise component" is that the self noise introduced
> by the mic is part of the total signal as a fixed percentage.  The
> noise introduced by the mic pre, at its current setting, is also a
> fixed percentage.
>
> The Rode NT-4 mic has 6.5 dB(A) LESS self noise than the Shure 183
> but the NT-4 produces a recording with MORE noise when MD record gain
> is set at 23-- which is typical for outdoors. Taking the mic self
> noise spec alone can be misleading, especially if one is interested
> in recording ambience.

I've pointed out that each mic also has a characteristic to it's self
noise. Some are smooth and hide easily, some sputter or crackle or
whatever and are easily annoying. This can negate spec differences. The
Shure seems to be of a fairly smooth variety, can be audible but not
really noticed. Don't know on the NT-4. Anyway, specs don't tell all.

What you are saying is that the mic sensitivity enters in as well as the
self noise. That is true, but it's easy to get too focused on that. The
self noise is usually controlling in terms of how quiet a site you can
record. Unless you are comparing large sensitivity differences between
two mics. Comparing the Shure against the MKH the story is different.

> I appreciate Walt's framing of mic self noise in relation to ambient
> sound levels because in some situations it is totally irrelevant. I
> can set levels for a cardinal at 15' or a snow blower down the block
> and play these recordings back without noise becoming a significant
> part of the experience.
>
> However, when recording ambience under quiet conditions-  mammals
> walking through the woods at night, the hush of dusk, the murmurings
> of a city at 3am on frigid winter morning-- the noise introduced by
> mic/mic pre combination is a very audible component of the
> recordings. I'm interested in the details of these spatial events so
> when I play these recordings, I'm amplifying the original event 50dB
> or more. In contrast, a frog or bird call played over many recordists
> speakers might be amplified ~6dB louder during home playback.
> Mic/pre Noise plays a very different role in these contrasting
> playback situations. Rob D.

Do not get to thinking all calls recorded were loud. When you factor in
distance this is not necessarily so. I record barking treefrogs from
great distances sometimes, for example. Greatest was over a mile. By ear
it's just a pulse in the quiet background noise that alerts me, the
telinga does better than my ears, but it's still imbedded in the
background and often the self noise. Many times I can't get closer,
though I do try.

One of the reasons why nature recording is misunderstood by music
recordists is that they hardly have to deal with self noise. They tend
to place more emphasis on max SPL specs. Their problem is at the other
end, too loud. At least for rock and such like.

And, yes, ambiance is where in nature recording you appreciate every dB
lower you can get in the self noise figure.

Walt




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