At 12:36 PM 2009-09-12, jmccubbinmd wrote:
>I'm relatively new to recording outdoor ambient sounds, but am very
>intrigued by it. I have done plenty of audio recording (amateur),
>but also have a background in astroimaging. I have been trying to
>solve the noise floor problem with microphones, as it seems to bug
>everyone to some degree. It just seems difficult and expensive to
>get rid of it. So that got me thinking.
>...
>Here is the comparison sample:
>
>http://m57.net/downloads/sfp/warblertest.mp3
It's a nice recording to start with, but the high-frequency noise
that you have on the original cut sounds tonal to me, not random.
I'm wondering where that's coming from. I don't THINK it's from the
702's mic pres. (I have the 722), but I can't imagine it coming from
the AT mics--though I have a DPA 4006 TL pair so I don't know.
Removing noise in audio, while similar to CCD image noise, is, as you
found out, not quite the same.
One of the best products in the field is Algorithmix Noise Free Pro.
If you use it enough to get a significant reduction in noise, even
this product can exacerbate any tonality in the noise. This tonality
I hear shows up in spectrum analysis in the 5-8 kHz region and you
can't remove that without damaging the bird call.
I've placed your warblertest back on my website with three sections now:
(1) Original
(2) a QUICK pass with Algorithmix Noise Free Pro sampling
from the audio w/o birds plus a sharp cutoff below 300 Hz.
(3) your original pass with Audacity.
I would try and figure out the source of this tonal noise whether
it's the recorder or the mics or the environment.
Here's the three-way comparison sample.
www.richardhess.net/clients/warbler/
Then right-click to download or whatever you wish to do with the file.
Cheers,
Richard
Richard L. Hess
Aurora, Ontario, Canada http://www.richardhess.com/
Detailed contact information: http://www.richardhess.com/tape/contact.htm
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