On Feb 25, 2009, at 1:00 AM, mrz wrote:
yes,i find it also not an absurd question. I had build a loop machine, and i did want to phase cancel the sound
is coming out of the speakers to be able recording and play again
new stuff over that loop in "realtime" (overdubbing). But as far as
i understand it is a really complex thing to do so as chuck allready
mentioned. But someone build allready a kind of "feedback canceller"
or is it simply not possible in the real world? Like, it's the best way simply EQ'ing your Soundsystem to have the
best result?
Best to do as bands do for singers or any other instrument when
feedback is not desired... use a cardioid microphone with low
sensitivity, and make the desired input signal much closer to the
microphone than the speakers. If possible, don't face the speakers
into the microphone at all. Even to achieve *some* feedback
cancellation is very difficult, and true cancellation is impossible
(except maybe theoretically for a totally known electro-acoustical
system, with same number of emitters and receivers). Feedback
avoidance is slightly more possible (e.g. by small frequency shifts).
At best, feedback suppression by narrow band filtering can only get
you a few extra db of gain before feedback pops up somewhere else.
Nick
all the best, moritz
On Mon, Feb 23, 2009 at 7:19 PM, Charles Henry czhenry@gmail.com
wrote: Hi, yohannesNo, it's not absurd. Tell us a little bit more about your application. I am out of the project game for now, but have some long term goals for solving this sort of problem.
For example, you send a sound out your speakers. You want to recieve a new sound from the room on microphone that is not the sound coming from the speakers.
This becomes a system identification problem. You need to find the delay between the speakers and microphone and the transfer function (a filter) between speakers and mic. Then, you digitally apply the filter and delay to your signals as they would be played and subtract that copy from the signal received by the mic.
Chuck
On Mon, Feb 23, 2009 at 4:02 PM, yohannes THIS_IS_POP@web.de wrote:
hello everybody,
maybe sounds absurd:
is it possible to cancel an whole signal of an mic input through phase-canceling?
if yes, how can i do dat in pd?
thanks a lot, yohannes
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