Dear Allan (and Pawel),
simply joining at zero crossings brings NO guarantee that you won't have click artifacts. If I take a sine wave and I cut it off at the zero crossing then I still have a 'sharp edge' at the zero crossing point where the signal snippet ends abruptly, and this will produce 'spectral splatter' and hence a potentially audible click artifact. You cannot completely avoid such transient artifacts at the joints of your cut and shuffled samples, but you can reduce them very considerably by cross-fading, and using something like a raised cosine ramp is likely to be better than a linear ramp. You are basically dealing with what signal engineers call a 'windowing' problem, and the literature on this is vast, so we could debate endlessly on what the 'ideal' approach would be, but a 3 ms cross-fade, as Pawel suggests, is likely to work well enough and is unlikely to raise too many eyebrows among potential reviewers.
Jan
Allan J Goldstein wrote: > I have tried looking for zero > crossings and making the cuts at these points, but > there is still the interference.
Cutting at zero crossings should solve the problem... But, do you just check for zero crossings, or for zero crossings in one direction? I mean, if you do one cut at a zero crossing where the signal goes from negative to positive, and the other one where the signal goes from positive to negative, then you can get a strong transient in a rejoined file: the signal will "bounce" from the zero line.
If this does not help, about a short (1-3 ms) crossfade - unless it interferes with your purpose.
Pawel
-- Pawel Kusmierek PhD Department of Physiology and Biophysics Georgetown University Medical Center The Research Building WP23 3970 Reservoir Road NW Washington, DC 20007 phone: +1 202 687-8851
-- Dr Jan Schnupp University of Oxford Dept. of Physiology, Anatomy and Genetics Sherrington Building - Parks Road Oxford OX1 3PT - UK +44-1865-272513 www.oxfordhearing.com