Hi Everyone, I am an engineer chiming in.
I have used this technique to clean up a signal. Technically, it is pretty simple to subtract out a "noise" signal. The hard part is getting a signal which is the exact "noise" you want to subtract. By exact I mean it has the equivalent gain, and timing and spectral content. If it is in the same frequency band as the target signal things get more difficult in a hurry. Does anyone have multiple channel recordings where the noise shows more prominently on one channel while the target bird shows better on another channel? I have Labview and can read *.wav files. I would be willing to spend some time messing with this if someone can provide a appropriate file. TomF retired Cornell Bioacoustics Engineer. At 01:00 AM 8/22/2009 -0400, you wrote: >Okay, last post for the night.... > >The more I read about this, the more and more it sounds really cool. > >So, you software and hardware engineer people out there - what do you >think? Can it work to better clean up night flight call data collection? >Heck, this could get you closer to that 90-95% positive detection figure >we'd all like to see. > ><http://plaza.ufl.edu/badavis/EEL6502_Project_1.html>http://plaza.ufl.edu/badavis/EEL6502_Project_1.html > >Sincerely, >Chris T-H > >Chris Tessaglia-Hymes wrote: >>I think the idea with adaptive noise cancellation is this: >> >>you have a dual microphone system. One channel is the primary channel >>(collecting the target sounds). The second channel is the "noise >>collection" channel. Through some mathematical algorithms, you subtract >>the noise collected in the "noise" channel from the primary channel >>(e.g., a different microphone aimed at collecting the cricket sounds or >>the katydid sounds, perhaps using a slightly lower gain setting, so as >>not to pick up distant flight calls being collected in the primary >>channel). The resulting signal in the primary channel should have reduced >>cricket and katydid sounds. Well, that's the theory, I guess. >> >>Here's an older paper abstract from 1975. Current technology can probably >>do this adaptive noise filtering in very real-time. >> >><http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1451965>http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1451965 >> >>Sincerely, >>Chris T-H -- NFC-L List Info: http://www.NortheastBirding.com/NFC_WELCOME http://www.NortheastBirding.com/NFC_RULES http://www.mail-archive.com/[email protected]/maillist.html --
