Brian,
I=92ll try and do some recordings at various gain levels with both high and=
low sensitivity using the internal and external mic. I live in a town home=
by a major road, however, so it may be too difficult to get the quiet I ne=
ed. I tried using a foam filled beanbag to deaden external noise, which see=
med to work very well, but our neighbor has an attic fan which is often run=
ning and which rumbles at 120 Hz 30dB. I can use the low pass filter as you=
suggested, but I think I=92ll need to wait for the road to quiet down.
Etiquette question: Is it best to quote the person I=92m responding to ever=
y time, or should I cut that out of my response?
Thanks again for all the great information and suggestions, everyone!
=96 Charles
> On Jun 13, 2015, at 11:50 AM, [naturerecordists] <nat=
> wrote:
>
> > I did some searching online but couldn't find details on whether high s=
ensitivity is artificially amplifying the signal or not with the PCM-M10,
>
> Charles,
>
> The signal level at the mic diaphragm is very small and needs to be
> amplified quite a lot before it can be recorded. Unfortunately no mic pre=
amp
> is perfect and the best we can get in practice is 12dB or 14dB equivalent=
> noise over the thermal noise of the air itself which is a whole new ball=
> game except it is taken as 0dB sound pressure level or 0Phons.
>
> This amplification is not "artificial" but essential, but the question is=
> how much? Up the bell of a trombone or near a drum, we can get something=
> like 120phons, so mic noise is not a problem, and we need to drop the gai=
n
> before the recorder or mixer overloads. This what the "low sensitivity"
> setting is for when mic noise is then not a problem anyway. The loudest
> audible noise will then probably be the recorder preamp noise drowning ou=
t
> the mic noise.
>
> With noisy wildlife we are up against overloads versus mic noise, but not=
> usually at the same time.
>
> For a lot of wildlife recording at very low sound levels, mic noise becom=
es
> audible, and the last thing we want is to add more noise in the recording=
> chain to the mic noise which is always with us, like the poor.
>
> > I'm a little confused by your statement about maximizing microphone his=
s. Can you please elaborate?
>
> You can't lose mic noise but you can avoid adding to it and this is why -=
> when listening from the end of the recording chain - the most audible
> _system noise_ you hear should be the electronic mic noise.
>
> > Very interesting, I'll have to try the dummy mic test. I picked up a us=
ed ME66 and I see that the impedance is listed at 200 ohms. Would I simply =
stick a 200 ohm resistor between pins 1 and 2 on the XLR adapter?
>
> Yes, except it is XLR pins 2 and 3. Pin 1 is ground.
>
> I'm not going to go into the "optimal noise impedance" of a mic, but I
> quoted 2000hms as that is what many preamps present to a mic. It is not
> critical.
>
> I've given you a bit of a problem here as you will need to compare the no=
ise
> as heard with a resistor with the mic hiss. This is where my "pile of
> bedclothes" test comes in. Forget the house rumbles and listen for hiss.=
>
> If you send me recordings of a few seconds with the mic and resistor at t=
he
> same high gain setting which doesn't overload with the rumble noise of th=
e
> house (put a bass cut in) I'll see if I can talk you through it.
>
> David Brinicombe
>
>
>
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