I will look to see if we do.. Sent from my iPhone
On Aug 24, 2009, at 9:54 AM, Thomas Fowler <[email protected]> wrote: > > 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 >> >> 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 >>> >>> 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 --
