My apologies to all for having hashed up the subject
line on this thread; I have no access to my email
archives today.
I downloaded the two files boom2.wav and bigboom2.wav.
I played them back, had a listen, and then subjected
them to some analysis. Firstly, let me say; Nice
recordings! Yes, they're clipped. But there's still
a good sense of space in them.
Here's what I get from the analysis:
The bottom line: clipping was electronic, and occur ed
subsequent to the conversion from M/S to stereo.
Assuming that the mic was being used to record in
stereo(I'm completely unfamiliar with the VP-88), the
clipping occurs about 1.8 dB below full scale.
I converted the recording from stereo back to M-S by:
M =3D 0.5*(L+R)
S =3D 0.5*(L-R)
The net result is that some of the clipping no longer
occurs near FS, but rather near zero. If the
microphone elements themselves were clipping, either
mechanically by virtue of the diaphragms hitting the
back plate, or by the electronics clipping, the
flat-topping would occur at FS.
I also observe that the two stereo channels have very
similar frequency responses. Assuming that the sound
field when the recording was diffuse (sounds have an
equal probability of coming from any direction), then
the long-term spectrum of both channels will be the
same, and that is what was observed.
In contrast, comparing the spectra of the M and S
channels shows that the S channel microphone rolls off
below about 300 Hz, relative to the M channel. Of
course, the M-channel no doubt rolls off too, when
compared to a flat microphone.
The am mount of clipping is really quite a lot.
During the time subsequent to the boom at time 7.912
seconds in bigboom2.wav, the waveform is clipped about
50% of the time. It's just not clipped at full scale.
I obviously can't tell you what clipped, but it seems
like you need to turn down the record level AT LEAST 6
dB relative to what was used.
Such a recording could be relatively responsive to
various "un-clipping" algorithms. Such algorithms
basically work by making up some audio to put in where
the waveform was clipped. That may not seem
aesthetically appealing, but in fact it can work very
well.
One final thing. Could you please send me some
thunder like that? I live on the California coast,
and we only get thunder about once a year.
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
------------------------------------------------------------------------
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/naturerecordists/
<*> To unsubscribe from this group, send an email to:
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
------------------------------------------------------------------------
|