actually, to control "image size" (apparent source width), one must control the interaural cross correlation rather finely, which in practice means controlling (or varying) inter-channel cross correlation (though with surround sound - ambisonic or otherwise, one actually has to control more speakers to govern the ear signals).
So, to go from an image as a point, to a more general, room-filling non-image sound, there is a variety of considerations and treatments. To enlarge an image, careful decorrelation of pairs (or more, see above) of signal feeds (to treat individual images, we are talking about this being on the encoding, not decoding end; in old fashioned terms, on the input side of the desk, not speaker feeds). This can be done with slight pitchshifts, taking harmonic slices and panning them, tiny delays, or a combination. Going from an enlarged image to a property of being everywhere really isnt a case of simply routing it to all available speakers - multichannel mono simply (because of precedence effects for off-centre listeners) pulls the perception to the nearest speaker. So the same principles of decorrelation as for image widening (and note - apparent source width can actually refer to up-down as well as lateral) should be used across the array. That way, you'd have a sense of the sound being everywhere, and nowhere in particular - which is what I think was the original intention cheers ppl Dr Peter Lennox School of Technology, Faculty of Arts, Design and Technology University of Derby, UK e: p.len...@derby.ac.uk t: 01332 593155 ________________________________________ From: sursound-boun...@music.vt.edu [sursound-boun...@music.vt.edu] On Behalf Of David Pickett [d...@fugato.com] Sent: 17 April 2012 23:27 To: Surround Sound discussion group Subject: Re: [Sursound] audio point / audio plenum At 15:26 17/04/2012, Gregorio Garcia Karman wrote: >Thanks for the inquisitive responses. The text was written in 1966 and >belongs to a composer from the circles of the BBC. It reads: > >"[one person] controls the volume of the total output of the platform >speakers, as well as the stereophonic motion of the sound to and from >between the loudpseakers, and the spread or growth of the sound from >audio-point to audio- plenum" > >For me it seems as if he would be describing some kind of >potentiometer by means of which the user can control the spread of >sound among the stereophonic image. From this description, it appears to me as though the person can control a mono signal in these ways: a) To pan between any two of the n loudspeakers. b) To increase the number of speakers carrying the signal from only one (audio-point) to all of them (audio-plenum). Without knowing exactly how the platform speakers are disposed it is impossible to say more. David _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound _____________________________________________________________________ The University of Derby has a published policy regarding email and reserves the right to monitor email traffic. If you believe this email was sent to you in error, please notify the sender and delete this email. Please direct any concerns to info...@derby.ac.uk. _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
