Subject: Re: high-frequency hearing in humans From: Andrew McGuiness <andymcguiness@xxxxxxxx> Date: Fri, 4 Feb 2011 16:34:13 -0800 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--0-1767008387-1296866053=:51747 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Others on the list will be more qualified to comment on this than I am, but= =0Acould the audible difference between sampling rates be due (at least in= part) to =0Adifferences in phase resolution? Frequencies at the Nyquist li= mit for a sampling =0Arate will be reproduced with only two possible phase = positions; frequencies a =0Alittle lower will have more, but not the full d= iscernible range of phase =0Adifference. Can't we hear phase differences wi= thin a few microseconds? A 44.1kHz =0Asampling rate will have a phase resol= ution of roughly 20 microseconds. As I =0Aunderstand it, phase differences = at frequencies approaching the Nyquist rate are =0Atranslated into level di= fferences (eg. a frequency component at the Nyquist =0Arate, sampled just a= fter a positive-going zero crossing will be recorded at a =0Alow level, and= the phase information will be reduced to 'positive'); in =0Apractice, over= sampling compensates for the loss of level, but not for temporal =0Aresolut= ion of phase.=0A=0AAndy=0A=0A Dr Andy McGuiness=0Aandymcguiness@xxxxxxxx= u=0Ahttp://open.academia.edu/AndyMcGuiness=0A=0A=0A=0A=0A=0ADate: Fri, 4= Feb 2011 07:41:39 -0700=0AFrom: "Maher, Rob" <rmaher@xxxxxxxx>= =0ASubject: Re: High-frequency hearing in humans=0A=0AAlthough the DSP port= ion of an oversampled system has precisely defined=0Aperformance characteri= stics, I remain highly skeptical that the=0Atransducers and analog electron= ics available to most users have ever=0Abeen evaluated in any meaningful wa= y outside the 20-22kHz bandwidth. I=0Aencourage everyone to be cautious ab= out drawing cause and effect=0Aconclusions for anecdotal reports. It may w= ell be that your colleague=0Ais hearing something, but the "how" and "what"= is not likely to be=0Arevealed by introspection alone.=0A=0ARob=0A=0A=0A = --0-1767008387-1296866053=:51747 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable <html><head><style type=3D"text/css"><!-- DIV {margin:0px;} --></style></he= ad><body><div style=3D"font-family:Courier New,courier,monaco,monospace,san= s-serif;font-size:12pt">Others on the list will be more qualified to commen= t on this than I am, but could the audible difference between sampling rate= s be due (at least in part) to differences in phase resolution? Frequencies= at the Nyquist limit for a sampling rate will be reproduced with only two = possible phase positions; frequencies a little lower will have more, but no= t the full discernible range of phase difference. Can't we hear phase diffe= rences within a few microseconds? A 44.1kHz sampling rate will have a phase= resolution of roughly 20 microseconds. As I understand it, phase differenc= es at frequencies approaching the Nyquist rate are translated into level di= fferences (eg. a frequency component at the Nyquist rate, sampled just afte= r a positive-going zero crossing will be recorded at a low level, and the phase information will be reduced to 'positive'); in practice, oversam= pling compensates for the loss of level, but not for temporal resolution of= phase.<br><br>Andy<br><div> </div>Dr Andy McGuiness<br>andymcguiness@xxxxxxxx= yahoo.com.au<br><span><a target=3D"_blank" href=3D"http://open.academia.edu= /AndyMcGuiness">http://open.academia.edu/AndyMcGuiness</a></span><div><br><= /div><div style=3D"font-family: Courier New,courier,monaco,monospace,sans-s= erif; font-size: 12pt;"><br><div style=3D"font-family: arial,helvetica,sans= -serif; font-size: 10pt;"><br><br>Date: Fri, 4 Feb 2011 07:41:= 39 -0700<br>From: "Maher, Rob" <<a ymailto=3D"mailto:rmaher= @xxxxxxxx" href=3D"mailto:rmaher@xxxxxxxx">rmaher@xxxxxxxx= .EDU</a>><br>Subject: Re: High-frequency hearing in humans<br><br>Althou= gh the DSP portion of an oversampled system has precisely defined<br>perfor= mance characteristics, I remain highly skeptical that the<br>transducers an= d analog electronics available to most users have ever<br>been evaluated in = any meaningful way outside the 20-22kHz bandwidth. I<br>encourage eve= ryone to be cautious about drawing cause and effect<br>conclusions for anec= dotal reports. It may well be that your colleague<br>is hearing somet= hing, but the "how" and "what" is not likely to be<br>revealed by introspec= tion alone.<br><br>Rob<br><br><br></div></div>=0A</div><br>=0A=0A=0A=0A = </body></html> --0-1767008387-1296866053=:51747--