?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=Helmholtz's+Piano+Strings%3A+Reverberation+of+Ripples+on+the+Tectorial+Membrane&rft.creator=Bell%2C+Andrew&rft.subject=Biophysics&rft.subject=Theoretical+Biology&rft.description=In+1857+Helmholtz+proposed+that+the+ear+contained+an+array+of+sympathetic+resonators%2C+like+piano+strings%2C+which+served+to+give+the+ear+its+fine+frequency+discrimination.+Since+the+discovery+that+most+healthy+human+ears+emit+faint%2C+pure+tones+(spontaneous+otoacoustic+emissions)%2C+it+has+been+possible+to+view+these+narrowband+signals+as+the+continuous+ringing+of+the+resonant+elements.+But+what+are+the+elements%3F+It+is+noteworhty+that+motile+outer+hair+cells+lie+in+a+precise+crystal-like+array+with+their+sensitive+stereocilia+in+contact+with+the+tectorial+membrane%2C+a+gelatinous+structure+with+an+observed+surface+tension.+This+paper+therefore+speculates+that+ripples+(surface+tension+waves)+on+the+lower+surface+of+the+tectorial+membrane+propagate+to+and+fro+between+neighbouring+cells.+This+mechanism+defines+a+surface+acoustic+wave+(SAW)+resonator%2C+and+relies+on+the+outer+hair+cells+directly+sensing+intracochlear+fluid+pressure+through+their+cell+bodies%3B+in+this+way+the+proposal+revisits+the+resonance+theory+of+hearing.+The+SAW+resonator+acts+as+a+regenerative+receiver+of+acoustic+energy%2C+a+topology+which+was+invoked+in+1948+by+Gold%2C+who+later+drew+the+analogy+to+an+'underwater+piano'+to+describe+the+cochlea's+problem+of+how+it+could+vibrate+with+high+Q+while+immersed+in+fluid.+The+proposal+also+gives+a+physical+description+of+the+cochlear+amplifier+postulated+by+Davis+in+1983.+An+active+array+of+resonating+cavities+driven+by+outer+hair+cells+can+explain+spontaneous+emissions%2C+the+shape+of+the+basilar+membrane+tuning+curve%2C+and+evoked+emissions%2C+among+others%2C+and+could+relate+strongly+to+music.+%0A%0AAt+levels+above+which+the+cochlear+amplifier+saturates%2C+ripples+on+the+tectorial+membrane+can+still+be+identified%2C+this+time+due+to+vibration+of+the+tectorial+membrane+against+the+sharp+vestibular+lip.+This+second+putative+mechanism+provides+time+delays+between+initiation+of+the+ripple+by+acoustic+pressure+variations+and+its+detection+by+the+inner+hair+cells%2C+and+so+represents+an+alternative+way+of+interpreting+the+traveling+wave.%0A%0AThus%2C+by+invoking+two+ways+of+generating+ripples+on+the+tectorial+membrane%2C+a+comprehensive+account+of+cochlear+mechanics+can+be+constructed%2C+unifying+a+resonance+theory+(at+low+levels)+with+a+traveling+wave+picture+(at+high+levels).%0A&rft.date=2001-08&rft.type=Preprint&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.identifier=http%3A%2F%2Fcogprints.org%2F1735%2F3%2FHelmholtz.pdf&rft.identifier=++Bell%2C+Andrew++(2001)+Helmholtz's+Piano+Strings%3A+Reverberation+of+Ripples+on+the+Tectorial+Membrane.++%5BPreprint%5D+++++&rft.relation=http%3A%2F%2Fcogprints.org%2F1735%2F