On Sun, 2006-01-29 at 13:40 +0100, Wolfgang Woehl wrote: > fons adriaensen <fons.adriaensen@xxxxxxxxx>: > > > There are certainly instruments that produce sound well > > above 20 kHz. Now to get 'beats' between two of those > > requires something non-linear - just summing them is not > > enough. Our ears are non-linear at high sound levels, so > > in a real performance this could happen. But I don't > > think it will be noticeable at any sane sound levels. > > Still don't understand the non-linear part here :/ > > I make 2 audio files with 400 and 500 hz sine tones and play > them along (out of ardour). There is clearly audible beat > frequency, a 100 hz hum and harmonics of that. You should also get 900Hz. They're the sum & difference frequencies. Apparently broadcast people called them sidebands? They're also the reason that barbershop quartets get "ringing" chords. I bumped into this page that explains non-linear distortion: http://www.isvr.soton.ac.uk/SPCG/Tutorial/Tutorial/Tutorial_files/Web-hearing-difference.htm bye John
