Re: [AUDITORY] Localizing smoke detectors - why is it so hard? ("Tollin, Daniel" )

Subject: Re: [AUDITORY] Localizing smoke detectors - why is it so hard?
From:    "Tollin, Daniel"  <Daniel.Tollin@xxxxxxxx>
Date:    Tue, 25 Jun 2013 04:07:54 -0600

Jennifer, Most alarms, such as the smoke alarm you mention, are designed to be hig= hly detectable and annoying. Thus, alarms generally have most of their pow= er in the ~1-3 kHz range where humans are most sensitive. However, while t= hese sounds are highly detectable, they are poorly localized due to the lim= ited usefulness of low frequency interaural delay cues at these intermediat= e frequencies (due to poor phase locking) and the paucity of interaural lev= el difference cues (i.e., the sounds have wavelengths that are not much sma= ller than the head diameter, thus the head doesn't produce much shadow). I= n other words these are some of the very worst sounds for accurate and prec= ise localization! Daniel J. Tollin, PhD Associate Professor University of Colorado School of Medicine Department of Physiology and Biophysics/Mail Stop 8307 Research Complex 1-N, Rm 7106 12800 East 19th Ave Aurora, CO 80045 Tel: 303-724-0625 Fax: 303-724-4501 ________________________________________ From: AUDITORY - Research in Auditory Perception [AUDITORY@xxxxxxxx= On Behalf Of Jennifer M. Groh [jmgroh@xxxxxxxx Sent: Tuesday, June 25, 2013 10:46 AM To: AUDITORY@xxxxxxxx Subject: Localizing smoke detectors - why is it so hard? 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

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