Re: On pitch and periodicity (was "correction to post") ("Nedra Floyd-Pautler, LLC" )


Subject: Re: On pitch and periodicity (was "correction to post")
From:    "Nedra Floyd-Pautler, LLC"  <nafp@xxxxxxxx>
Date:    Wed, 3 Aug 2011 00:29:33 +0000
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

------=_Part_43329_1108792853.1312331373911 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Thanks to all of you who responded to my inquiry on the practical significa= nce of auditory illusions. You've given me much to think about, listen to, = and read. I appreciate your generous spirits, and I'm pursuing your suggest= ions. My initial curiosity was about whether hearing aid design could someh= ow use auditory illusions (or what they tell us about how the brain hears) = to help the HA wearers focus their listening attention or in some other way= improve the hearing experience. As I understand it, a hearing-aid wearer i= s more bothered by background noise than non-wearers. But why would wearing= a hearing aid impact the brains ability to attenuate sound or focus attent= ion? And if it does, is there something in auditory illusions that would be= useful in solving the problem. You've given me many other things to think = about as well.=20 Again, thanks,=20 Nedra Floyd-Pautler=20 www.thenedra.com=20 ----- Original Message ----- From: "ita katz" <itakatz@xxxxxxxx>=20 To: AUDITORY@xxxxxxxx=20 Sent: Tuesday, August 2, 2011 12:15:11 PM=20 Subject: Re: On pitch and periodicity (was "correction to post")=20 Richard,=20 I almost totally agree with you. My intention wasn't to imply that the audi= tory system has some arithmetic-related capabilities --- I was just mention= ing the simple arithmetic principles.=20 In other words (and relating to a different phenomenon), although the traje= ctory of a tennis ball flying through air can be modeled by some complex pa= rtial differential equations, I would not state that a person catching a fl= ying tennis ball have some part of its brain actually integrating these equ= ations.=20 The only question I wanted to ask, is why there are many references to the = missing fundamental as being an auditory illusion, while the periodicity is= not an illusion at all. I agree that saying that the auditory system perce= pts periodicity is oversimplifying and not 100% correct.=20 Thanks for your comments.=20 On Tue, Aug 2, 2011 at 8:49 PM, Richard F. Lyon < DickLyon@xxxxxxxx > wrote:= =20 At 5:55 PM +0300 8/2/11, ita katz wrote:=20 The periodicity is determined by the least-common-multiple of the periodici= ties of the present harmonics, so if (for example) a sound is composed of s= ines of frequencies 200Hz, 300Hz, and 400Hz, the periods are 5msec, 3 1/3ms= ec, and 2.5msec, so the least-common-multiple is 10msec (2 periods of 5msec= , 3 periods of 3.33msec, and 4 periods of 2.5msec), which is of course the = periodicity of the sum of the sines, or in other words 100Hz. (actually it = is the same as the greatest-common-divisor of the frequencies).=20 Ita, that explanation is sort of OK, but as written implies that the audito= ry system has the ability to do number-theory operations on periods (or fre= quencies), and depends on there being harmonics present and separately meas= ureable.=20 It would be much more robust to say that "The pitch is determined based on = an approximately common periodicity of outputs of the cochlea," which I bel= ieve is consistent with your intent.=20 Why is this better? First, it doesn't say the periodicity is determined; wh= at is determined is the pitch (even that is a bit of stretch, but let's go = with it). Second, it doesn't depend on whether the signal is periodic, that= is, whether harmonics exist. Third, it doesn't depend on being able to iso= late and separately characterize components, harmonic or otherwise. Fourth,= it doesn't need "multiples" (or divisors), but relies on the property of p= eriodicity that a signal with a given period is also periodic at multiples = of that period, so it only needs to look for "common" periodicities--which = doesn't require any arithmetic, just simple neural circuits. Fifth, it admi= ts approximation, so that things like "the strike note of a chime" and nois= e-based pitch can be accommodated. Sixth, it recognizes that the cochlea ha= s a role in pitch perception. It's still not complete or perfect, but I thi= nk presents a better picture of how it actually works, in a form that can b= e realistically modeled.=20 Is this "tortured use of existing signal processing techniques" as Randy pu= ts it? I don't think so. Is it "a unique way to do frequency analysis and t= o meet the dictum in biology that 'form follows function'"? Sure, why not? = But why call it "frequency analysis"? How about "a unique way to do sound a= nalysis" (if by "unique" we mean common to many animals)?=20 I do have some sympathy for Randy's concern that we are far from a complete= understanding, and that hearing aids are not as good as they would be if w= e understood better, but yes, he sounds way too harsh in overblowing it so.= I'm wondering what's behind that, and whether it's just confusion about al= l the confusing literature on pitch perception, which I agree is a complica= ted mess -- or is the problem, indicated by Randy's previous posts, just th= at he doesn't understand basic linear systems and signal processing, and th= at's why it all seems "tortured"?=20 Dick=20 ------=_Part_43329_1108792853.1312331373911 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable <html><head><style type=3D'text/css'>p { margin: 0; }</style></head><body><= div style=3D'font-family: Arial; font-size: 12pt; color: #000000'>Thanks to= all of you who responded to my inquiry on the practical significance of au= ditory illusions. You've given me much to think about, listen to, and read.= I appreciate your generous spirits, and I'm pursuing your suggestions. My = initial curiosity was about whether hearing aid design could somehow use au= ditory illusions (or what they tell us about how the brain hears) to help t= he HA wearers focus their listening attention or in some other way improve = the hearing experience. As I understand it, a hearing-aid wearer is more bo= thered by background noise than non-wearers. But why would wearing a hearin= g aid impact the brains ability to attenuate sound or focus attention? And = if it does, is there something in auditory illusions that would be useful i= n solving the problem. You've given me many other things to think about as = well.<div><br></div><div>Again, thanks,</div><div>Nedra Floyd-Pautler</div>= <div>www.thenedra.com<br><br><hr id=3D"zwchr"><b>From: </b>"ita katz" &lt;i= takatz@xxxxxxxx&gt;<br><b>To: </b>AUDITORY@xxxxxxxx<br><b>Sent: </b= >Tuesday, August 2, 2011 12:15:11 PM<br><b>Subject: </b>Re: On pitch and pe= riodicity (was "correction to post")<br><br><div dir=3D"ltr">Richard,<br><b= r>I almost totally agree with you. My intention wasn't to imply that the au= ditory system has some arithmetic-related capabilities --- I was just menti= oning the simple arithmetic principles. <br> <br>In other words (and relating to a different phenomenon), although the t= rajectory of a tennis ball flying through air can be modeled by some comple= x partial differential equations, I would not state that a person catching = a flying tennis ball have some part of its brain actually integrating these= equations.<br> <br>The only question I wanted to ask, is why there are many references to = the missing fundamental as being an auditory illusion, while the periodicit= y is not an illusion at all. I agree that saying that the auditory system p= ercepts periodicity is oversimplifying and not 100% correct.<br> <br>Thanks for your comments.<br><br><br><div class=3D"gmail_quote">On Tue,= Aug 2, 2011 at 8:49 PM, Richard F. Lyon <span dir=3D"ltr">&lt;<a href=3D"m= ailto:DickLyon@xxxxxxxx" target=3D"_blank">DickLyon@xxxxxxxx</a>&gt;</span> w= rote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;borde= r-left:1px #ccc solid;padding-left:1ex;"> At 5:55 PM +0300 8/2/11, ita katz wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex"> The periodicity is determined by the least-common-multiple of the periodici= ties of the present harmonics, so if (for example) a sound is composed of s= ines of frequencies 200Hz, 300Hz, and 400Hz, the periods are 5msec, 3 1/3ms= ec, and 2.5msec, so the least-common-multiple is 10msec (2 periods of 5msec= , 3 periods of 3.33msec, and 4 periods of 2.5msec), which is of course the = periodicity of the sum of the sines, or in other words 100Hz. (actually it = is the same as the greatest-common-divisor of the frequencies).<br> </blockquote> <br> Ita, that explanation is sort of OK, but as written implies that the audito= ry system has the ability to do number-theory operations on periods (or fre= quencies), and depends on there being harmonics present and separately meas= ureable.<br> <br> It would be much more robust to say that "The pitch is determined based on = an approximately common periodicity of outputs of the cochlea," which I bel= ieve is consistent with your intent.<br> <br> Why is this better? &nbsp;First, it doesn't say the periodicity is determin= ed; what is determined is the pitch (even that is a bit of stretch, but let= 's go with it). &nbsp;Second, it doesn't depend on whether the signal is pe= riodic, that is, whether harmonics exist. &nbsp;Third, it doesn't depend on= being able to isolate and separately characterize components, harmonic or = otherwise. &nbsp;Fourth, it doesn't need "multiples" (or divisors), but rel= ies on the property of periodicity that a signal with a given period is als= o periodic at multiples of that period, so it only needs to look for "commo= n" periodicities--which doesn't require any arithmetic, just simple neural = circuits. &nbsp;Fifth, it admits approximation, so that things like "the st= rike note of a chime" and noise-based pitch can be accommodated. &nbsp;Sixt= h, it recognizes that the cochlea has a role in pitch perception. &nbsp;It'= s still not complete or perfect, but I think presents a better picture of h= ow it actually works, in a form that can be realistically modeled.<br> <br> Is this "tortured use of existing signal processing techniques" as Randy pu= ts it? &nbsp;I don't think so. &nbsp;Is it "a unique way to do frequency an= alysis and to meet the dictum in biology that 'form follows function'"? &nb= sp;Sure, why not? &nbsp;But why call it "frequency analysis"? &nbsp;How abo= ut "a unique way to do sound analysis" (if by "unique" we mean common to ma= ny animals)?<br> <br> I do have some sympathy for Randy's concern that we are far from a complete= understanding, and that hearing aids are not as good as they would be if w= e understood better, but yes, he sounds way too harsh in overblowing it so.= &nbsp;I'm wondering what's behind that, and whether it's just confusion ab= out all the confusing literature on pitch perception, which I agree is a co= mplicated mess -- or is the problem, indicated by Randy's previous posts, j= ust that he doesn't understand basic linear systems and signal processing, = and that's why it all seems "tortured"?<br> <br> Dick<br> </blockquote></div><br></div> </div></div></body></html> ------=_Part_43329_1108792853.1312331373911--


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