Subject: Sources of DPOAEs. From: "reinifrosch@xxxxxxxx" <reinifrosch@xxxxxxxx> Date: Fri, 20 Jan 2012 17:14:24 +0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>------=_Part_3936_19432393.1327079664762 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Dear colleagues, Most oto-acoustic emissions (OAEs) appear to differ fundamentally from the = reflection of electric signals at the end of coaxial cables. "AFAIK", the g= roup delays of SFOAEs (stimulus-frequency OAEs) agree with the hypothesis t= hat they are generated by outer hair cells (OHCs) in the basal-slope zone o= f the "active" (low-sound-pressure-level, healthy-cochlea) excitation peak = of the sine-tone wave. These OHCs feed mechanical energy into the apically = directed travelling wave (TW); some of that energy generates a basally dire= cted TW, and so an OAE. DPOAEs (distortion-product OAEs, especially "low-si= de" ones, frequency f_DP =3D 2f_1 - f_2, where f_2 > f_1), on the other han= d, have been found to have two distinct sources. The first source is the ov= erlap region of the two excitation peaks of the two sine-tone waves with fr= equencies of f_1 and f_2. The second DPOAE source has been claimed to be th= e reflection of the cochlear TW travelling from the generation place to the= (more apical) best place of that f_DP wave. Question: Is it possible that = this second DPOAE is not due to a coaxial-cable-like reflection either, but= is generated (similarly to the mentioned SFOAEs) by OHCs which feed energy= into the apically directed f_DP wave? Reinhart Frosch, CH-5200 Brugg. reinifrosch@xxxxxxxx . ------=_Part_3936_19432393.1327079664762 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>Dear colleagues,</FONT= ></P> <P><FONT size=3D2>Most oto-acoustic emissions (OAEs) appear to differ funda= mentally from the reflection of electric signals at the end of coaxial cabl= es. "AFAIK", the group delays of SFOAEs (stimulus-frequency OAEs)= agree with the hypothesis that they are generated by outer hair cells (OHC= s) in the basal-slope zone of the "active" (low-sound-pressure-level, healt= hy-cochlea) excitation peak of the sine-tone wave. These OHCs feed mec= hanical energy into the apically directed travelling wave (TW); some of tha= t energy generates a basally directed TW, and so an OAE. DPOAEs (distortion= -product OAEs, especially "low-side" ones, frequency f_DP =3D 2f_1 - f_2, w= here f_2 > f_1), on the other hand, have been found to have two distinct= sources. The first source is the overlap region of the two excitation peak= s of the two </FONT><FONT size=3D2>sine-tone waves with frequencies of= f_1 and f_2. The second DPOAE source has been claimed to be the refle= ction of the cochlear TW travelling from the generation place to the (= more apical) best place of that f_DP wave. Question: Is it possible that th= is second DPOAE is not due to a coaxial-cable-like reflection either, but i= s generated (similarly to the mentioned SFOAEs) by OHCs which feed energy i= nto the apically directed f_DP wave?<BR>Reinhart Frosch,<BR>CH-5200 Br= ugg.<BR>reinifrosch@xxxxxxxx . </FONT></P></div></body></html> ------=_Part_3936_19432393.1327079664762--