My first msg hasn't come through yet, so I am resending it. Sorry if the first one does show up. ----------------------------------------------------------------------- At 04:52 PM 6/21/01 -0700, Chris wrote: It is actually more complicated. The dynamics of the room would have to be accounted for, which makes it many times more difficult than in the headset case. Also, to be able to cancel the noise in several directions you need more drivers and mikes. I once toyed with the idea of a feedback-controlled stereo system to completely elliminate the dynamics of your listening room and hear those of the recording hall, for example. The idea was: when you record, you place mikes separated 3-4" apart in one of the audience chairs, mimicking the directionality of human ears mounted on a cranium :-) . In fact, you install several such sets of mikes, all with a slightly different orientation wrt sound source. Then, at home, you put on a headset that doesn't cover your ears, but it has a second set of mikes like the ones used for recording, and some orientation sensing device. The stereo/DSP's job is the following: to project on your headset's mikes sound waves that produce identical local pressure at your ears (feedback control ideas would be used) to those that were received at the recording hall by the set of mikes that most closely matches your current head position. Voila`, Panoramic Sound. The algorithms for doing this exist already, and, while slightly complicated for the ocasional home stereo hobbyist, they are within the grasp of any grad student in the control/DSP/cancellation field. They involve the estimation of the reproduction room's characteristics, feedback control and active cancellation ideas. Somebody must be developing this exact idea somewhere. It is just a logical step given the state of DSP and active cancellation technology. Carlos. -------------------------------------------------------------- Carlos E. Murillo-Sanchez carlos_murillo(a)nospammers.ieee.org