Re: High-frequency hearing in humans ("reinifrosch@xxxxxxxx" )


Subject: Re: High-frequency hearing in humans
From:    "reinifrosch@xxxxxxxx"  <reinifrosch@xxxxxxxx>
Date:    Wed, 26 Jan 2011 13:51:45 +0000
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

------=_Part_2994_30851970.1296049905845 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hello! My posting sent yesterday, involving the cochlear amplifier (CA), was based= on a misunderstanding. I tried to describe the biophysical cause of good h= igh-frequency hearing, not its evolutionary advantage. Nevertheless, one co= chlear-mechanics effect may be relevant: If the CA would amplify low-frequ= ency tones by 40 dB, then the basilar-membrane displacement amplitude would= be so large (even at fairly low sound-pressure levels) that the organ of C= orti would be damaged. Reinhart Frosch, Dr. phil. nat., CH-5200 Brugg. reinifrosch@xxxxxxxx . ----Urspr=C3=BCngliche Nachricht---- Von: robert.zatorre@xxxxxxxx Datum: 25.01.2011 21:24 An: <AUDITORY@xxxxxxxx> Betreff: Re: High-frequency hearing in humans Greetings Isn't it parsimonious to assume that humans--and other creatures--have=20 high frequency hearing for the simple reason that there is lots of=20 useful information out there in the natural environment in the higher=20 frequency range? Yes it's also useful for localization etc., but=20 identifying a source would be at least as critical. Many critters that we might want to eat, run away from, or merely be=20 aware of make noises in that range with their vocal tracts, wings, legs=20 etc (birds, crickets, etc); and others who are bigger still might at=20 least make HF noise by stepping on leaves/branches etc and hence leave=20 tell-tale cues in high frequencies. Plus lower frequencies might=20 occasionally be masked by noise (water, wind...) so one would want to=20 detect the presence of others even in a noisy environment. So it would be adaptive to be able to hear them, would it not? That=20 seems like the simplest explanation to me. RZ -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Robert J. Zatorre, Ph.D. Montreal Neurological Institute 3801 University St. Montreal, QC Canada H3A 2B4 phone: 1-514-398-8903 fax: 1-514-398-1338 e-mail: robert.zatorre@xxxxxxxx web site: www.zlab.mcgill.ca ------=_Part_2994_30851970.1296049905845 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, sans-serif; font-size: small; margin:0; padding:0;} div.bwmail p { margin:0; padding:0; } div.bwmail table { font-family: Trebuchet MS,Arial,Helvetica, sans-serif; f= ont-size: small; } div.bwmail li { margin:0; padding:0; } --> </style> </head><body><div class=3D'bwmail'><P><FONT size=3D2>Hello!</FONT></P> <P><FONT size=3D2>My posting sent yesterday, involving the cochlear amplifi= er (CA),&nbsp;was based on a misunderstanding. I tried to describe the&nbsp= ;biophysical cause of good high-frequency hearing, not its evolutionary adv= antage. Nevertheless, one cochlear-mechanics effect may be relevant:&nbsp;I= f the &nbsp;CA would amplify low-frequency tones by 40 dB, then&nbsp;the ba= silar-membrane displacement amplitude would be so large (even at fairly low= sound-pressure levels) that the organ of Corti would be damaged.<BR><BR>Re= inhart Frosch,<BR>Dr. phil. nat.,<BR>CH-5200 Brugg.<BR>reinifrosch@xxxxxxxx= ch .</FONT><BR><BR></P> <BLOCKQUOTE><FONT size=3D2>----Urspr=C3=BCngliche Nachricht----<BR>Von: rob= ert.zatorre@xxxxxxxx<BR>Datum: 25.01.2011 21:24<BR>An: &lt;AUDITORY@xxxxxxxx= MCGILL.CA&gt;<BR>Betreff: Re: High-frequency hearing in humans<BR><BR>Greet= ings<BR><BR>Isn't it parsimonious to assume that humans--and other creature= s--have <BR>high frequency hearing for the simple reason that there is lots= of <BR>useful information out there in the natural environment in the high= er <BR>frequency range? Yes it's also useful for localization etc., but <BR= >identifying a source would be at least as critical.<BR><BR>Many critters t= hat we might want to eat, run away from, or merely be <BR>aware of make noi= ses in that range with their vocal tracts, wings, legs <BR>etc (birds, cric= kets, etc); and others who are bigger still might at <BR>least make HF nois= e by stepping on leaves/branches etc and hence leave <BR>tell-tale cues in = high frequencies. Plus lower frequencies might <BR>occasionally be masked b= y noise (water, wind...) so one would want to <BR>detect the presence of ot= hers even in a noisy environment.<BR><BR>So it would be adaptive to be able= to hear them, would it not? That <BR>seems like the simplest explanation t= o me.<BR><BR>RZ<BR><BR>-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<BR><BR>Robert J. = Zatorre, Ph.D.<BR>Montreal Neurological Institute<BR>3801 University St.<BR= >Montreal, QC Canada H3A 2B4<BR>phone: 1-514-398-8903<BR>fax: 1-514-398-133= 8<BR>e-mail: robert.zatorre@xxxxxxxx<BR>web site: <A href=3D"http://www.zl= ab.mcgill.ca">www.zlab.mcgill.ca</A></FONT></BLOCKQUOTE></div></body></html= > ------=_Part_2994_30851970.1296049905845--


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