=C2=A0
stancourtney <> wrote:
> ...I am not sure what frequency response I need.
While I'm not at all sure about Sasquatch recording, your recording problem=
is
similar to many in that you don't know exactly what you need, because you
haven't done it before. Given that you describe having heard/felt the soun=
ds
that you are interested in recording, I suppose that we would call that nea=
r
infrasound in the terminology of the web pages at:
http://www.esrl.noaa.gov/psd/programs/infrasound/infrasonic.html
I had originally assumed that you want to record sounds for later analysis =
but
not I'm guessing that you also would like to listen to the sound. That bri=
ngs
up the problem of reproducing the recorded LF sounds, but that's another pr=
oblem
for another forum.
I have had some experiences with the Sound Devices MM-1 in which it had
insufficient bass response. Unfortunately I no longer have access to any o=
f
that data so I can't say anything specific, other than that other preamps m=
ay
give better performance in this application.
In contrast to another reply, I would say that the choice of microphone sho=
uld
be the first thing to check, and not the recorder; if the low frequency sou=
nds
don't make it through the microphone then it doesn't matter what the record=
er
does.
I do a lot of measurements of recording equipment. Looking over the few
omnidirectional microphones in my collection, my Audio Technica AT3032 is d=
own
only a few tenths of a dB at 10 Hz, a microflown p-u 'match' probe rolls of=
f
below 100 Hz, a Schoeps Mk2 rolls off at about 23 Hz, Earthworks M30 is dow=
n
just 0.2 dB at 10 Hz, Shure MX183s roll off at about 40 Hz (I'm sure that's=
the
adapter), a microphone based on the Knowles FG capsule is down 4 dB at 10 H=
z, a
studio projects C4 capsule on a Rode NT5 body was down 0 at 10 Hz (but not=
nearly as good as that on the C4 body).
It seems likely that the Rode NT5 with their new omni capsule would be a go=
od,
low-cost microphone for low-frequency recording.
Your qyery has caued me to expand the range over which I usually test frequ=
ency
response. I usually go down to 10 Hz but I can extend those measurements d=
own
to 1 Hz or so. I have just one portable recorder at present and that's th=
e
Zoom H2, because it records 4 channels. If you use the microphone inputs i=
t
starts to roll off at 40 Hz and it's about 32 dB down at 1 Hz. Going in th=
rough
the line inputs it's 3 dB down at 7 Hz and 22 dB down at 1 Hz.
I want to point out that, just because the recorder or the microphone rolls=
off
a bit doesn't mean that you can't make a usable recording. It's quite
reasonable to equalize out the frequency response roll-offs for either the=
purposes of listening or analysis of the files. If I wanted to make a reco=
rding
that goes down to 10 Hz, I'd just use what I've got. If I wanted to go dow=
n to
1 Hz I'd have to do some modification of my existing equipment. Precisely =
what
I would do would depend on whether I could take a laptop into the recording=
situation.
If you would like to see any of these measurements let me know and I'll pub=
lish
some graphs to our web site.
Eric
From: stancourtney <>
To:
Sent: Tue, July 27, 2010 7:17:56 PM
Subject: [Nature Recordists] Re: Infrasound microphone
Thanks for all the replies.
Although I am interested in all nature recording I do have a special
interest in sasquatch research. Most serious researchers shy away from
any discussion of the subject. I can understand that view.
Many bigfoot / sasquatch researchers have had experiences in areas of
bigfoot sightings with what they consider to be infrasound. Symptoms
have been various from tingling, paralysis, nausea, fear and dread. Some
of these symptoms may also be associated with pheromones.
I recently had a major experience in the Blue Mountains of Washington
State. I won't discuss it here but you can read my post at:
http://www.stancourtney.com/wordpress/2010/07/26/infra-sound-in-the-blues/=
recording I do have a special interest in sasquatch research. Most
serious researchers shy away from any discussion of the subject. I can
understand that view. Many bigfoot / sasquatch researchers have had
experiences in areas of bigfoot sightings with what they consider to be
infrasound. Symptoms have been various from tingling, paralysis, nausea,
fear and dread. Some of these symptoms may also be associated with
pheromones. I recently had a major experience in the Blue Mountains of
Washington State. I won't discuss it here but you can read my post at:
http://www.stancourtney.com/wordpress/2010/07/26/infra-sound-in-the-blue\
s/>
So I am not sure what frequency response I need. The effects I felt were
both outside and inside my Jeep. They were very intense but nothing
showed up on my recordings while using a MKH 20 microphone and the 722
recorder.
Thanks for the comments and suggestions.
Stan Courtney
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