Phase Cancellation and Hello

[RobbiedeJong]

Hi guys,

Not sure which section to post this in so have posted it more than once as it is important to me sorry.

Im new to the froum. A little about me first - Im studying Audio System Design at Southampton Solent University (UK) in my final year.

To the crux of the matter. For my final year project I have set myself the challenge of designing and making a unit to detect and supress acoustic feedback in an audio system - both digital and analogue. As feedback is a sinewave created by the delay in a system in correlation with a specific frequencey I have come up with a theory in order to supress it without using standard filters.

I am looking into using phase cancellation in order to do this. I was wondering if there was anyone who had expertise in this field or research or just any ideas really as I'm just getting off the ground with this.

Thanks in advance for any help.

Regards


Robbie de Jong

[moonbaby]

I used to work for the guy who started Sabine Systems, one of the first companies to manufacture anti-feedback devices. I have been doing live sound for too many (30+) years, and I can tell you with pretty good certainty that there is a good deal of phase-shifting going on when feedback occurs. In fact, that was one of the major hurdles that the owner of Sabine had to clear to make his product effective.

Feedback is not a "simple sinewave", and since it is an interaction of 2 (or more) transducers (a mic and a loudspeaker), and can easily force the electronics in the equation (both the mic preamp and the power amp) into a situation where they are both massively overdriven, resulting in the generation of clipped waveforms (good-bye sine wave!) and even more phase shift. A moving microphone aggravates this

The companies that have invested so much time and resources into this abbhoration have circuits that are patented to protect their business model. It's really not "off-the-shelf" technology. But good luck to ya!