Thanks, Walt. I have a few questions:
I get the 80Hz noise in all my recordings. Is this "normal noise" for a
Portadisc and MKH 30/40? Also, is the "low shelf filter" you used to knock=
it out equivalent to using an FFT filter in Adobe Audition?
I have the same questions about the 18kHz noise.
Concerning the distortion noise that shouldn't be there - can you describe=
it or tell me where it is on the sonogram? I didn't identify it and would=
like to be able to hear/see it as you did. If you worked on the file from=
my original post (DawnChorus.mp3) the distortion may have occurred because=
I may have inadvertently encoded the MS signal twice, using Audition's
Channel Mixer's "Mid-Side to L-R" pre-set. I later posted an original file=
(www.danablackmer.com/AudioFiles/DawnChorusMS.wav) and an mp3 file
(www.danablackmer.com/AudioFiles/DawnChorusXY.mp3) that I know wasn't
double encoded.
You also said that you added and trained a denoise filter (Spark XL TC
Denoise) to decrease this distortion noise. Would this be similar to
Audition's Noise Reduction filter (a filter that works by capturing a noise=
reduction profile from a segment of about 0.5-1" of noise-only sound and
then using that to profile to reduce the noise in the entire recording).
Thanks again for your helpful response.
Dana
At 04:53 PM 6/25/2006 -0400, you wrote:
>Posted by: "Dana Blackmer"
><danablackmer%40comcast.net> danablackmerph=
d
>
> > Thanks in advance to anyone who can give me some suggestions. My
> > hope is that the more experienced of you can educating the less
> > experienced of us in the science and art of what to do after you've
> > finished recording.
>
>Hopefully I have nothing to do but transfer the recording.
>
>I downloaded the file, then put it in my sound editing program, in this
>case I ended up doing it using Peak.
>
>I then set up a empty filter bank (TC Works FX Machine) with a realtime
>sonogram (from TC Works SparkXL) in the last slot (after everything).
>All filtering was monitored not just by ear but by sonogram. This is
>important if you wish to minimize effects on wanted sounds.
>
>Listening to the sample while watching the sonogram three things were
>obvious, and you requested another.
>
>1. There was some low frequency noise below 80 hz, so I added the equium
>plugin (Elemental Audio) and a low shelf filter in it to knock out that.
>A drop of 18dB in it's level. This was a nearly inaudible change.
>
>2. There was a sound band up above 16kHz, probably noise. This was cut
>down 18dB using a high shelf filter in equium. Though for most it's
>inaudible.
>
>3. There is some sort of distortion noise, I believe this is what you
>are identifying as steady insects but it's not insects. Though a number
>of distant calls were also changed by whatever it is. You need to find
>and eliminate the source of this as it should not be there at all and
>cannot be removed entirely with filtering. It should not have occurred.
>I have a portadisc and M/S MKH-40/30 and this is not normal to them. I
>did add and train a denoise filter (Spark XL TC Denoise) to it and
>removed as much as I could. Note this did cut down some wanted sound,
>particularly some of the high pitched birds chattering and dulled the
>recording a little. More experimentation with training the filter might
>yield a better setting. The unwanted sound was cut down by about 12dB
>
>4. I toned down the fly a little bit by placing a parametric equalizer
>notch in equium set narrow and at 205Hz (the second fly). I farther
>toned the first fly down by using a notch filter at 215Hz in equium.
>(the two flys are not running their wings at quite the same beat rate)
>This did not eliminate the flys, though that could be done by a similar
>method as their buzzing does not overlap any other wanted sound in
>frequency.
>
>This left a cleaner recording, though many calls are badly off due to
>whatever was wrong with your sample.
><http://loscan.home.mindspring.com/DawnChorus-es.mp3>http://loscan.home.mi=
ndspring.com/DawnChorus-es.mp3
>
>I agree with others, unless your purpose is to present a cleaned call of
>a single species, limit your filtering primarily to things like man made
>noise (though one could say that belongs too).
>
>If you can ID that problem in the recording, which could be when
>recorded but is more likely either in transfer to computer or in
>encoding to mp3, the recording sounds like it's pretty good.
>
>Always focus on getting the best recording in the field. Assume you
>can't remove anything with filtering.
>
>Walt
>
>
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