Apologies for the length of this, but as I don't know what was going on, I
don't know what was important, so I need to give full details.
Bernie Krause wrote 24 Aug 2003:
> From: Wild Sanctuary <>
>
> Remember that infrasound is hard to impossible to reproduce with any
> ease.
>
As a matter of curiosity, I have managed to "record" some infrasound that
wasn't there! Some sort of equipment malfunction and I don't know what.
I was recording a lyrebird (what else for Syd Curtis!) in perfect recording
conditions. Not a leaf stirring even on the tops of the rainforest canopy
40 metres above me. I noticed the meter on the Tascam DA-P1 was registering
a fluctuating but continuous signal of up to about -50dB for considerable
periods of time, but not 100 % of the time. There was no ambient sound that
I could detect, and I couldn't hear what this was when listening to the
recording.
I was using a Rode NT4 stereo mic, which I had bought only a couple of days
before with cables I had made myself. I also made a recording using a
Sennheiser ME20 mono mic on a long cable. (No such problem there that I
noticed.)
With old age, my hearing has deteriorated, particularly in the higher
frequencies. I sought the help of Vicki Powys, Tape Editor for the
Australian Wildlife Sound Recording Group. Using Peak LE I took a digital
signal from the Tascam to the Audiomedia III sound card in my Mac G3, and
without any filtering, etc., copied selected extracts to an Audio CD and to
a data CD. I hoped that the data CD would be effectively a clone of my DAT.
(Was that a reasonable expectation?)
I sent th two CDs to our Tape Editor, and here in part is her advice:
"First I tried the Audio CD, listening to just part of each track.
All four tracks have some strange added sound, a sort of crackly sound that
is more apparent with the louder notes. The last track was least affected.
"Then I tried the Peak files, same crackly distortion effect with louder
notes. Plus another strange thing happening - those trembling db levels in
quiet passages that you described was happening on your Tascam meter, has
also transferred to the Peak files. All I can actually hear is very slight
low rumbling, not normally anything I'd be concerned about. BUT when I
analyzed a short section on AudioGraph, this noise shows up as extremely low
frequency, presumably sub-sonic 'cos I can't actually hear it. I'll have to
double check later to see if it happened on all 4 tracks to any degree, or
not.
"I can only surmise there is something actually wrong with the TASCAM.
Can't be the Rode in particular 'cos the same slight crackling effect
happened with BOTH mics and presumably with different leads. And can't be
to do with the transfer to your computer 'cos you said you noticed the
levels on the Tascam doing strange things while you were actually recording.
"(And it's not my computer 'cos I've been working on sound files all day
and they are all OK.)"
I'm guessing that the omnipresent crackling distortion, to which Vicki
refers is largely or entirely high frequency, and thus not apparent to me.
But I certainly agree with later comment that I'm wasting my time doing any
recording until the problems are fixed.
So all my gear is now with Musiclab for checking, and I await their expert
advice. I can but hope they find something. Meanwhile if any
Naturerecordist using a Tascam has ever experienced anything like this and
can offer advice that I can pass on to Musiclab, I'd be very grateful
indeed.
Further observations:
I found that there is a way I can hear that infrasound. The Tascam has
a facility whereby you can put it in play mode and then press 'fast forward'
or 'rewind' and it then plays at a fast speed. How fast, I do not know, and
no doubt the sound is distorted, but it is useful for finding some
particular part of a tape. When I do that, that infrasound becomes a very
audible rattle.
I have little technical knowledge, and not much soldering skill, but on
this occasion, I made up twin cables a couple of metres long to connect the
Rode mic to the Tascam. Recording seemed to work OK when I used two of my
old long cables. I endeavoured to copy them. Three-pin XLR plugs, and I
soldered the shield to the same terminals as in my old cables. Appeared to
work OK at home.
After the recording trip, when I examined the Y-cord supplied with the Rode,
I found that there is also a wire soldered from the shield terminal to the
actual clip of the plug. This I had not done with my cables. (I have now.)
Finally, when inserting the Y-cord into the Rode mic., considerable force is
required to compress a rubber O-ring, before the plug locks in place. It
can appear to be fully in, and only by pulling can one find that it is not
locked. I can't now be certain that I did have it locked in place.
Anyone care to comment?
Cheers
Syd Curtis in Australia
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