Of course, to hear recorded infrasound, it is necessary to somehow
"speed up" the signal to something above 30Hz for most speakers to
transmit the signal. But there is a "mystery" out there, for sooth.
Once, while leading a bioacoustic trip to Alaska, 8 of us were
standing at the shoreline of Pt. Aldolphus on the northern tip of
Chichagoff Island (in Icy Straights about 40 miles w. of Juneau) one
evening, when we felt a very low frequency signal coming from
who-knows-where. It was felt viscerally and it was a VERY strong
signal! At first we thought it was some airborne humpback signal.
Then anthroposonic. Then we gave up. It happened twice. Then never
again. And I couldn't get my hydrophone hooked up in time to capture
it (a hydrophone also works as a mic...particularly if you want to
capture infrasound). Anyway, it is weird. And, yes, it remains a
mystery many folks have reported - certainly in North America.
(Someone must be testing those weapons of mass destruction no one can
seem to find.)
Bernie
> 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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--
Wild Sanctuary, Inc.
P. O. Box 536
Glen Ellen, CA 95442
707-996-6677 tel
707-996-0280 fax
http://www.wildsanctuary.com
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