Subject: Re: Helmholtz and combination tones. From: "Richard F. Lyon" <DickLyon@xxxxxxxx> Date: Thu, 4 Aug 2011 22:36:41 -0700 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY><!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"><!-- blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 } --></style><title>Re: Helmholtz and combination tones.</title></head><body> <div>It has been done. You get a stronger pitch percept when the phases give strong envelope modulation, and less pitch percept otherwise, such as for random phases. I don't have a ref handy, but I saw a figure in something I was looking at just the other day.</div> <div><br></div> <div>John Pierce's 1991 JASA paper is another example of the pitch depending on the phasing of high harmonics.</div> <div>http://asadl.org/jasa/resource/1/jasman/v90/i4/p1889_s1</div> <div><br></div> <div>Dick</div> <div><br></div> <div><br></div> <div>At 7:07 PM -0700 8/4/11, James Johnston wrote:</div> <blockquote type="cite" cite>I don't know if it's been done, but it would be interesting to see what happens when you set up the various harmonics for a missing-fundamental probe in different phases, and see what happens when they do and do not all cross zero at the same time.<br> </blockquote> <blockquote type="cite" cite>On Thu, Aug 4, 2011 at 6:16 PM, William Hartmann <<a href="mailto:hartmann@xxxxxxxx">hartmann@xxxxxxxx</a>> wrote:<br> <blockquote>Dear List,<br> <br> A recent post from Randy Randhawa says, "Consider that even Helmholtz had to appeal to non-linear processes (never really described) in the auditory system to account for the missing fundamental and combination tones."<br> <br> Because this comment raises questions about what Helmholtz did and did not describe, I would draw attention to Appendix XII in "On the Sensation of Tone." There Helmholtz begins with the simple harmonic oscillator dynamical equation and adds a quadratic term to the restoring force, clearly conceived as just the second term in an expansion in the displacement. He solves this to first and second order in small quantities and finds that the second order term leads to combination tones, which could include a missing fundamental.<br> <br> An interesting feature of his solution is that summation tones are much weaker than difference tones, which agrees with observation. Specifically, for two frequencies f1 and f2, the summation tone amplitude goes as 1/[(f2+f1)^2-fo^2] and the difference tone amplitude goes as 1/[(f2-f1)^2-fo^2], where fo is the natural frequency of the oscillator.<br> <br> Bill Hartmann<br> <br> PS Singularities in the amplitudes occur because there is no damping in the dynamical equation and resonances are unbounded.<br> </blockquote> </blockquote> <blockquote type="cite" cite><br> <br> <br> --<br> </blockquote> <blockquote type="cite" cite>James D. (jj) Johnston</blockquote> <blockquote type="cite" cite>Independent Audio and Electroacoustics Consultant</blockquote> <div><br></div> </body> </html>