Subject: Re: [AUDITORY] Localizing smoke detectors - why is it so hard? From: "Richard F. Lyon" <dicklyon@xxxxxxxx> Date: Tue, 25 Jun 2013 10:43:05 -0700 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--047d7b676b3cbf08ab04dffe0fe5 Content-Type: text/plain; charset=ISO-8859-1 Jennifer, I believe the answer is primarily in the transducer: to make the beeper cheep, they use a resonant transducer, which has a slow buildup at the onset and makes the resulting signal not very broadband at all, depriving you of all ITD cues. And they make the beeps so brief that you don't have much chance to turn your head and vary the ILD cue; and so far apart in time that you get impatient waiting for the next beep for your next chance to find it. And you're in a very echoic environment where the echos of the narrowband beep off the walls make standing nulls to further confuse the ILD cue. The beepers on carts in airports have the same problem. They can come up behind you and make a loud beeping noise, but you have no idea they are there -- they seem to be designed to defeat any possible usable spatial cues. There ought to be a law ... oh, wait, there probably is, contributing to the problem. Dick On Tue, Jun 25, 2013 at 1:46 AM, Jennifer M. Groh <jmgroh@xxxxxxxx> wrote: > Dear List, > > I am writing a book for a general audience on how the brain processes > spatial information ("Making Space"). The chapter on hearing covers many > topics in sound localization, but there is one that I'm currently still > quite puzzled about: why it is so hard to localize a smoke detector when > its battery starts to fail? Here is what I have considered so far: > > - To my ear, the chirp sounds high frequency enough that ILD cues should > be reasonably large. > > - At the same time, it seems to have a broad enough bandwidth, and in any > case it has onset-and-offset cues, that ITD cues should be usable. > > - A possibility is that the chirp is too brief, and that limits dynamic > feedback, i.e. changes in ITD and ILD as the head turns during a sound. > However, in my laboratory we have obtained excellent sound localization > performance in head-restrained monkeys and human subjects localizing sounds > that are briefer than the reaction time to make an orienting movement. > > - An additional possibility is that we have too little experience with > such sounds to have assembled a mental template of the spectrum at the > source, so that spectral cues are of less use than is normally the case. > > I'm leaning towards a combination of the last two factors, which together > would render the cone of confusion unresolved for these stimuli. > > Thoughts? > > Best wishes, > > --Jennifer Groh > > -- > Jennifer M. Groh, Ph.D. > > Professor > Department of Psychology and Neuroscience > Department of Neurobiology > Center for Cognitive Neuroscience > > > B203 LSRC, Box 90999 > Durham, NC 27708 > > 919-681-6536 > www.duke.edu/~jmgroh > --047d7b676b3cbf08ab04dffe0fe5 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div>Jennifer,<br><br>I believe the answer is primarily in= the transducer:=A0 to make the beeper cheep, they use a resonant transduce= r, which has a slow buildup at the onset and makes the resulting signal not= very broadband at all, depriving you of all ITD cues.=A0 And they make the= beeps so brief that you don't have much chance to turn your head and v= ary the ILD cue; and so far apart in time that you get impatient waiting fo= r the next beep for your next chance to find it.=A0 And you're in a ver= y echoic environment where the echos of the narrowband beep off the walls m= ake standing nulls to further confuse the ILD cue.<br> <br>The beepers on carts in airports have the same problem.=A0 They can com= e up behind you and make a loud beeping noise, but you have no=A0 idea they= are there -- they seem to be designed to defeat any possible usable spatia= l cues.<br> <br></div><div>There ought to be a law ... oh, wait, there probably is, con= tributing to the problem.<br></div><div><br></div>Dick<br><br></div><div cl= ass=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Tue, Jun 25, 2013= at 1:46 AM, Jennifer M. Groh <span dir=3D"ltr"><<a href=3D"mailto:jmgro= h@xxxxxxxx" target=3D"_blank">jmgroh@xxxxxxxx</a>></span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex">Dear List,<br> <br> I am writing a book for a general audience on how the brain processes spati= al information ("Making Space"). The chapter on hearing covers ma= ny topics in sound localization, but there is one that I'm currently st= ill quite puzzled about: why it is so hard to localize a smoke detector whe= n its battery starts to fail? =A0Here is what I have considered so far:<br> <br> - To my ear, the chirp sounds high frequency enough that ILD cues should be= reasonably large.<br> <br> - At the same time, it seems to have a broad enough bandwidth, and in any c= ase it has onset-and-offset cues, that ITD cues should be usable.<br> <br> - A possibility is that the chirp is too brief, and that limits dynamic fee= dback, i.e. changes in ITD and ILD as the head turns during a sound. =A0 Ho= wever, in my laboratory we have obtained excellent sound localization perfo= rmance in head-restrained monkeys and human subjects localizing sounds that= are briefer than the reaction time to make an orienting movement.<br> <br> - An additional possibility is that we have too little experience with such= sounds to have assembled a mental template of the spectrum at the source, = so that spectral cues are of less use than is normally the case.<br> <br> I'm leaning towards a combination of the last two factors, which togeth= er would render the cone of confusion unresolved for these stimuli.<br> <br> Thoughts?<br> <br> Best wishes,<br> <br> --Jennifer Groh<br> <br> -- <br> Jennifer M. Groh, Ph.D.<br> <br> Professor<br> Department of Psychology and Neuroscience<br> Department of Neurobiology<br> Center for Cognitive Neuroscience<br> <br> <br> B203 LSRC, Box 90999<br> Durham, NC 27708<br> <br> 919-681-6536<br> <a href=3D"http://www.duke.edu/~jmgroh" target=3D"_blank">www.duke.edu/~jmg= roh</a><br> </blockquote></div><br></div> --047d7b676b3cbf08ab04dffe0fe5--