Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!sundc!potomac!jtn From: jtn@potomac.ads.com (John T. Nelson) Newsgroups: comp.sys.amiga,comp.sys.mac,comp.sys.atari.st,rec.music.makers,rec.music.synth Subject: Re: Sonic Holography. Message-ID: <2666@potomac.ads.com> Date: Fri, 4-Dec-87 23:11:29 EST Article-I.D.: potomac.2666 Posted: Fri Dec 4 23:11:29 1987 Date-Received: Wed, 9-Dec-87 23:31:14 EST References: <7536@eddie.MIT.EDU> <2476@gryphon.CTS.COM> Organization: Advanced Decision Systems, Arlington VA Lines: 43 Summary: Ball bouncing up in ptich... Xref: mnetor comp.sys.amiga:11975 comp.sys.mac:10674 comp.sys.atari.st:6633 rec.music.makers:1168 rec.music.synth:2095 > Plus, there is an audio illusion I've been looking for, for quite > a while now. Basically it is an ever increasing tone. > > There was a display at the Ontario Science center, ohh, 12 years or so > ago, about MC Escher, that had a ball bouncing "up" an ever increasing > staircase, with this tone, going up in pitch. > > It went up in pitch for the 1/2 hour I stood there. :-) > > Any clues ? Yup. I saw a film of this back in the 70's. The film was created at Bell Labs. The effect is easy to reproduce. The bouncing sound is the sum of several frequencies from 0 - 20 Khz weighted by a gaussian distribution with the hump of the curve starting at the lowest frequencies. Now increase the volumn on adjacent frequencies by sliding the distribution up the scale. Your ear assumes that the loudest frequency is the one that you heard the last time but increased in pitched. In fact it heard all frequnecies but focused on the most predominant (loudest). As you slide the volumn weights towards the high frequencies the gaussian distribution wraps around to the low end of the frequency spectrum and the tone that your ear thought it was hearing (the high end), fades off into the distance. By this time though it has picked up the increasing volumn of the lower tones and is following them up the scale. Repeat endlessley. All this time we were watching a film of a ball bouncing up and Escheresque staircase and feeling like a bunch of laboratory mice. -- John T. Nelson UUCP: sun!sundc!potomac!jtn Advanced Decision Systems Internet: jtn@potomac.ads.com 1500 Wilson Blvd #512; Arlington, VA 22209-2401 (703) 243-1611 Sine Visa Ars Nihil Est