Re: mechanical cochlear model ("reinifrosch@xxxxxxxx" )


Subject: Re: mechanical cochlear model
From:    "reinifrosch@xxxxxxxx"  <reinifrosch@xxxxxxxx>
Date:    Thu, 3 Jun 2010 09:54:51 +0000
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

------=_Part_1246_999835.1275558891555 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hello Peter, =20 Thank you for your protest. The role of the round window is interesting: du= ring a sine-tone of 10 kHz, say, the local wave number of the travelling s= urface wave at the base of the human cochlea is ~0.8 mm^-1; local waveleng= th =3D 2pi/k =3D 8 mm. Width of basilar membrane (BM): w =3D 0.1 mm; radius= of roughly half-circular strong-liquid-motion regions just above and just = below BM: r =3D 0.2 mm. At the round window, there is no liquid motion and = no liquid sound pressure. During a sine-tone of lower frequency, 0.5 kHz, s= ay, a (slow) travelling surface wave would require liquid motion and liquid= sound pressure in the whole near-base cochlear-channel cross-section, also= at the round window. Because of the softness of that window, however, a si= gnificant liquid sound pressure on its inside cannot be built up, so at low= frequency, there is indeed no significant slow travelling surface wave at = the base of the mammalian cochlea, if the round window is not blocked. This= can be confirmed, e.g., via Recio and Rhode (2000), "Basilar membrane resp= onses to broad-band stimuli", JASA 108, 2281-2298.=20 =20 Reinhart. ----Urspr=C3=BCngliche Nachricht----------------------- Von: pwj.vanhengel@xxxxxxxx Datum: 02.06.2010 12:46 An: <AUDITORY@xxxxxxxx> Betreff: Re: mechanical cochlear model Dear Martin, =20 interesting results no doubt, but once again I must protest against the con= clusions. As I have stated before it is not so easy to abolish or greatly r= educe the traveling wave in the cochlea. Any motion of the fluid, in combin= ation with the flexibility of the BM, will cause a traveling wave, even if = you severely influence the boundary conditions. Oversimplification of fluid mechanics in the cochlea has led to erroneous c= onclusions before... Just a warning against drawing conclusions too rapidly. Regards, Peter -------------------------------------------------- Reinhart Frosch, Dr. phil. nat., r. PSI and ETH Zurich, Sommerhaldenstr. 5B, CH-5200 Brugg. Phone: 0041 56 441 77 72. Mobile: 0041 79 754 30 32. E-mail: reinifrosch@xxxxxxxx . ------=_Part_1246_999835.1275558891555 Content-Type: text/html;charset="UTF-8" Content-Transfer-Encoding: quoted-printable <html><head><style type=3D'text/css'> <!-- div.bwmail { background-color:#ffffff; font-family: Trebuchet MS,Arial,Helv= etica; font-size: 12px; margin:0; padding:0;} div.bwmail p { margin:0; padding:0; } div.bwmail table { font-family: Trebuchet MS,Arial,Helvetica; font-size: 12= px; } div.bwmail li { margin:0; padding:0; } --> </style> </head><body><div class=3D'bwmail'><P>Hello Peter,</P> <P>&nbsp;</P> <P>Thank you for your protest. The role of the round window is interesting:= during a&nbsp;sine-tone of 10 kHz, say, the local wave number of the&nbsp;= travelling surface wave at the base of the human cochlea &nbsp;is ~0.8 mm^= -1; local wavelength =3D 2pi/k =3D 8 mm. Width of basilar membrane (BM): w = =3D 0.1 mm; radius of roughly half-circular strong-liquid-motion regions ju= st above and just&nbsp;below BM: r =3D 0.2 mm. At the round window, there i= s no liquid motion and no liquid sound pressure. During a sine-tone of lowe= r frequency, 0.5 kHz, say, a (slow) travelling surface wave would require l= iquid motion and liquid sound pressure in&nbsp;the whole near-base cochlear= -channel cross-section, also at the round window. Because of the softness o= f that window, however, a significant liquid sound pressure on its inside c= annot be built up, so at low frequency, there is indeed&nbsp;no significant= slow travelling surface wave at the base of the mammalian cochlea, if the = round window is not blocked. This can be&nbsp;confirmed, e.g., via Recio an= d Rhode (2000), "Basilar membrane responses to broad-band stimuli", JASA 10= 8, 2281-2298.&nbsp;</P> <P>&nbsp;</P> <P>Reinhart.</P> <P><BR>----Urspr=C3=BCngliche Nachricht-----------------------<BR>Von: pwj.= vanhengel@xxxxxxxx<BR>Datum: 02.06.2010 12:46<BR>An: &lt;AUDITORY@xxxxxxxx= GILL.CA&gt;<BR>Betreff: Re: mechanical cochlear model<BR><BR></P> <DIV>Dear Martin,</DIV> <DIV>&nbsp;</DIV> <DIV>interesting results no doubt, but once again I must protest against th= e conclusions. As I have stated before it is not so easy to abolish or grea= tly reduce the traveling wave in the cochlea. Any motion of the fluid, in c= ombination with the flexibility of the BM, will cause a traveling wave, eve= n if you severely influence the boundary conditions.</DIV> <DIV>Oversimplification of fluid mechanics in the cochlea has led to errone= ous conclusions before...</DIV> <DIV>Just a warning against drawing conclusions too rapidly.<BR></DIV> <DIV>Regards,</DIV> <DIV>Peter<BR>--------------------------------------------------</DIV> <DIV>Reinhart Frosch,<BR>Dr. phil. nat.,<BR>r. PSI and ETH Zurich,<BR>Somme= rhaldenstr. 5B,<BR>CH-5200 Brugg.<BR>Phone: 0041 56 441 77 72.<BR>Mobile: 0= 041 79 754 30 32.<BR>E-mail: reinifrosch@xxxxxxxx .<BR></DIV></div></body= ></html> ------=_Part_1246_999835.1275558891555--


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