Subject: envelope extraction From: "Hornsby, Benjamin Wade Young" <ben.hornsby@xxxxxxxx> Date: Mon, 23 Feb 2009 10:55:05 -0600 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>This is a multi-part message in MIME format. ------_=_NextPart_001_01C995D7.7A50826B Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hi all, I hope the answer to this question is not too obvious but,... We have recently been talking about auditory processing models, in specific, temporal processing models, many of which incorporate an envelope extraction stage. To do this I've seen in many cases the use of half wave rectification followed by a low pass filter. The cutoff for this filter is generally a pretty low frequency, say around 50 Hz or so. A colleague suggested that the actual cutoff frequency should be based on the assumed time constant of the system or subsystem being evaluated. I've been trying to determine the physiologic rational for such a low frequency filter (slow time constant) in models of auditory processing. Neural processing limitations like the refractory period of the neuron are much faster than this. Anyone have a reference or two that might help explain the physiologic rational for this low frequency filter cutoff? =20 Thanks much, =20 Ben =20 =20 ------_=_NextPart_001_01C995D7.7A50826B Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable <html xmlns:o=3D"urn:schemas-microsoft-com:office:office" = xmlns:w=3D"urn:schemas-microsoft-com:office:word" = xmlns=3D"http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv=3DContent-Type content=3D"text/html; = charset=3Dus-ascii"> <meta name=3DGenerator content=3D"Microsoft Word 11 (filtered medium)"> <style> <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; margin-bottom:.0001pt; font-size:12.0pt; font-family:"Times New Roman";} a:link, span.MsoHyperlink {color:blue; text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {color:purple; text-decoration:underline;} span.EmailStyle17 {mso-style-type:personal-compose; font-family:Arial; color:windowtext;} @xxxxxxxx Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in;} div.Section1 {page:Section1;} --> </style> </head> <body lang=3DEN-US link=3Dblue vlink=3Dpurple> <div class=3DSection1> <p class=3DMsoNormal><font size=3D2 face=3DArial><span = style=3D'font-size:10.0pt; font-family:Arial'>Hi all,<o:p></o:p></span></font></p> <p class=3DMsoNormal><font size=3D2 face=3DArial><span = style=3D'font-size:10.0pt; font-family:Arial'>I hope the answer to this question is not too obvious = but,… We have recently been talking about auditory processing models, in = specific, temporal processing models, many of which incorporate an envelope extraction = stage. To do this I’ve seen in many cases the use of half wave rectification followed by a low pass filter. The cutoff for this filter is generally a = pretty low frequency, say around 50 Hz or so. A colleague suggested that the = actual cutoff frequency should be based on the assumed time constant of the system or subsystem being evaluated. I’ve been trying to determine the = physiologic rational for such a low frequency filter (slow time constant) in models of = auditory processing. Neural processing limitations like the refractory period of = the neuron are much faster than this. Anyone have a reference or two that = might help explain the physiologic rational for this low frequency filter = cutoff?<o:p></o:p></span></font></p> <p class=3DMsoNormal><font size=3D2 face=3DArial><span = style=3D'font-size:10.0pt; font-family:Arial'><o:p> </o:p></span></font></p> <p class=3DMsoNormal><font size=3D2 face=3DArial><span = style=3D'font-size:10.0pt; font-family:Arial'>Thanks much,<o:p></o:p></span></font></p> <p class=3DMsoNormal><font size=3D2 face=3DArial><span = style=3D'font-size:10.0pt; font-family:Arial'><o:p> </o:p></span></font></p> <p class=3DMsoNormal><font size=3D2 face=3DArial><span = style=3D'font-size:10.0pt; font-family:Arial'>Ben<o:p></o:p></span></font></p> <p class=3DMsoNormal><font size=3D2 face=3DArial><span = style=3D'font-size:10.0pt; font-family:Arial'><o:p> </o:p></span></font></p> <p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span = style=3D'font-size: 12.0pt'><o:p> </o:p></span></font></p> </div> </body> </html> ------_=_NextPart_001_01C995D7.7A50826B--