in my understanding of the interference tube, the sound coming from the
front arrives undisturbed to the mic capsule, without any gain given by the
structure. On the contrary, sounds entering the tube from other directions
enter through multiple holes in the sides and do different length travel
paths to the capsule; this way they are reduced by the summing not in phase=
.
with a shotgun mic you don't have additional gain, but only reduction of
sounds coming out of axis.
the only chance to increase gain is to use beam forming with multiple
microphones or use a parabolic reflector to "concentrate" the acoustic
energy coming from the front on the mic capsule in the focus.
Gianni
2014-07-17 16:23 GMT+02:00 'John Crockett'
[naturerecordists] <>:
>
>
> I wouldn't think that impedance matching would be an issue with the
> PCM-M10. It has a very high impedance input (I think it's 20k ohms), so
> very little loss from voltage division.
>
> I was thinking as I drove to work this morning that it makes sense that
> the overall signal would be higher using the built-ins on the PCM-M10
> because they are grabbing sound from all directions - they are
> omnidirectional microphones. Whereas the shotgun microphone (I wish we ha=
d
> a less violent word) is rejecting sound from the sides. So if there is
> abundant sound energy coming from the sides, the omnis will be picking it
> up and the "shotgun" will be reducing the level of those sounds, so the
> overall recording level could be much lower using the "shotgun," more tha=
n
> just the 3 dB that can be attributed to the lower sensitivity of the NTG2=
.
> But if the only sound source is, say, a single bird, and the "shotgun" is
> pointing right at it, then I would think the "shotgun" microphone would
> result in a higher level than the omnis, even if it is a little less
> sensitive.
>
> Does that make sense?
>
> John
>
>
> >> I have had a Sony PCM M10 for several years and I recently purchased a
> >> Rode NTG2 shotgun mic. It works and both channels show equal recording
> >> levels, but I am disappointed to find that the actual decibal levels
> >> shown are quite a bit lower than when I just use the on-board
> >> microphones.
> >
> > Don,
> >
> > This has been answered, but another reason for lower level nay be
> > impedance
> > matching. You can get over this by using a matching pre-amp, but low
> level
> > is not a problem except perhaps for listening at the time of recording.
> >
> > One of the things I bang on about with digital recording is that it is
> > better to record low than risk hitting the limiter with unexpected loud
> > sounds. Peaking to as low as -20DB is fully recoverable afterwards.
> >
> > The best check is the pile of bedclothes test. Record "silence" with bo=
th
> > setups in a quiet room under absorbent material and listen to the hiss
> > levels at high gain afterwards.
> >
> > As has been said, recorded volume is not the problem, it is the relatio=
n
> > of
> > bird to hiss which sets the limit.
> >
> > David Brinicombe
> >
> >
> >
> >
> > ------------------------------------
> > Posted by:
> > ------------------------------------
>
> >
> > "While a picture is worth a thousand words, a
> > sound is worth a thousand pictures." R. Murray Schafer via Bernie Kraus=
e.
> >
> >
> > ------------------------------------
> >
> > Yahoo Groups Links
> >
> >
> >
>
> John Crockett
>
> Let us live in harmony with Earth
> And all creatures,
> That our lives may be a blessing.
>
>
>
--
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Universit=E0 degli Studi di Pavia
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