Hi all,
Not sure if this has been touched on before (I'm a new member to this group)
but you may wish to consider using Frequency Analysis techniques to reduce
unwanted noise such as AC noise.
We have done a lot of work on engine noises, and find Adobe Audition
invaluable for this....frequency domain work.
If you have a recording with the AC noise 'contaminating' something, then I
would load these sounds into something like Audition, and actually look at
the Frequency Analysis to try to identify exactly where in the spectrum they
are occurring, rather than trying to guess with multiple parametric EQ's.
Mechanical noises such as AC will usually be quite obvious by their constant
'lines' on the display if they are 'drone' like sounds.
E.g. Loading in your MP3 exhibits these lines - the strongest remaining
'drone' is roughly at 480.5Hz J but several others are visible. These can be
removed quite easily...
Audition enables you to actually edit the audio using the frequency analysis
display itself, so just visually identify the areas you want to reduce in
volume, draw a selection box around them, and you are able to
increase/decrease the amplitude of just those selected frequencies. You can
also draw irregular shapes, rather than simple boxes, so it is feasible to
alter rising/falling frequencies as well as static drones.
You are still faced with the problem of the AC and your subject material
sharing the same frequencies in places, and this technique can be time
consuming if your contamination has lots of harmonics/lines, but this kind
of 'surgical' removal of noises can often be much more accurate and less
damaging to the rest of the sound.
Tim.
From:
On Behalf Of Rob Danielson
Sent: 03 August 2010 21:52
To:
Subject: Re: [Nature Recordists] Wolf pup vs Coyotes...
Hi Mitch--
Interesting to hear a chorus from Massachusetts. The pitch of the
calls is lower and the energy rate is a little slower than the
Wisconsin packs I'm accustom to. An alpha does seem to be trying to
contact pack members, perhaps to determine their location. The
individual who calls to the left towards the end seems to make a
confirmation bark, but the pack doesn't respond. The yotes should
become more vocal into the Fall, especially the pups. It doesn't
sound to me like there are the typical 4-5 pups in that pack.
AC is a huge contributor to the grungescape this time of year isn't
it?. Using several parametric EQ "notches" to reduce specific drones
of the AC equipment might make the recording feel less "thin" than
using high pass filtering. There's a pretty nice Parametric EQ plug
that comes with Reaper that has unlimited bands.
I'm not sure how I would address stereo with two shotgun mics, but it
seems like there is quite a bit of left-right "cross-talk" in the
stereo image. Can you describe how you have the mics positioned?
Have you tried placing a baffle or other separator between them? Rob
D..
= = = =
At 3:04 PM -0400 8/3/10, Mitch Hill wrote:
>
>
>Back about a month ago if my memory serves me correctly, someone (Mark?)
>had a recording of wolf or coyote pups they were hoping to identify. As I
>recall, we all agreed they were wolf sounds in his recording.
>
>Monday, August 2nd at 1:30-2:00AM in the wee early hours of the morning, I
>happened to catch our local Coyote pack in full song in the tree farm and
>have finally managed to get a decent recording. I think this recording in
>comparison affirms the wolf conclusion to his recording.
>
>As this recording starts, there is about a 27 second delay of tree frogs
>and pond frogs until what I presume is the alpha female coyote of the pack
>puts out a call. this is followed by a 35-40 second delay, and she calls
>again and almost immediately a second voice joins hers and for nearly a
>minute, all the rest of the pack as well as a few coyotes in the distance
>joins in.
>
>The recording is in stereo, you can get a feel of distance and direction to
>some of the further out coyotes combined with the sound of the frogs make
>this a very unique recording I think...
>
>This recording was made with a Tascam Dr680 recorder and a pair of
>Sennheiser ME66 microphones which were pointed in the general direction of
>the Cape Cod Academy buildings about 1/4 mile beyond my location, the
>coyotes were between my location and the Academy with its air conditioners
>roaring...
>Therefore I have run this audio through a 450hz highpass filter to get rid
>of most of the air conditioner noise however as the coyote sounds start at
>about 500 hz and go up in frequency, there is still a bit of the air
>conditioner droning bleeding through at the bottom end of the frequencies
>of this recording.
>
>You can hear this recording here:
>
>Direct play using on-line audio streamer:
><http://www.4shared.com/audio/vX2dfvam/CCCoyotes01.html>http://www.4shared.
com/audio/vX2dfvam/CCCoyotes01.html
>
>Download MP3 file to play on your own system:
><http://dc229.4shared.com/download/vX2dfvam/CCCoyotes01.mp3>http://dc229.4s
hared.com/download/vX2dfvam/CCCoyotes01.mp3
>
>Your comments please, I'm a learner at this field of endeavor and your
>feedback and critiques are important to me...
>--
>
>Mitch
>
><http://www.4shared.com/dir/UTASxktL/wildlife.html>http://www.4shared.com/d
ir/UTASxktL/wildlife.html
>
>Shadow's area:
><http://www.4shared.com/dir/ecfWjyZb/Shadow.html>http://www.4shared.com/dir
/ecfWjyZb/Shadow.html
>
>
--
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