[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [AUDITORY] Localizing smoke detectors - why is it so hard?

You are right, Dick! A series of recent papers on "transposed AM sounds" by Les Bernstein and Tino Trahiotis show very clearly that periodically interrupted high-frequency carriers are localizable based on ITD.

On 6/27/13 12:37 PM, "Richard F. Lyon" <dicklyon@xxxxxxx> wrote:

Ewan, thanks for your paper reference; very relevant.

You wrote there, "ITD dominance is shown indirectly in findings that head movements are highly effective for localizing low-frequency targets but not narrow-band high-frequency targets."

I agree.  But it doesn't address what you could do with wide-band high-frequency targets.  If the alarms used 3 kHz, but chopped on and off, with not such a high-Q resonance, they would probably have good enough onsets to help you make use of ITD, yes? 

I often see people disregarding ITD as a powerful cue above 1 kHz or so; but the basis for that is only that it's not a usable cue for sine waves and other narrow-band signals.  Wideband clicks and noises are easy to localize, even if simulated with only ITD.


On Wed, Jun 26, 2013 at 1:52 PM, Ewan A. Macpherson <ewan.macpherson@xxxxxxxxxx> wrote:
Richard F. Lyon wrote, On 6/25/2013 1:43 PM:


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;

It also turns out that front/back location is much more readily disambiguated by head turning in stimuli that carry low-frequency ITD than in those carrying only high-frequency ILD (such as the ~3-kHz, more-or-less pure tones from smoke detectors). The dynamic ILD cue does not seem to be able to beat the phantom spectral cue due to the narrow high-frequency peak in the spectrum. This is true under anechoic conditions, and presumably would be even worse in reverberation.