Re: High-frequency hearing in humans (Bob Masta )


Subject: Re: High-frequency hearing in humans
From:    Bob Masta  <audio@xxxxxxxx>
Date:    Thu, 27 Jan 2011 09:02:12 -0500
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

On 26 Jan 2011 at 17:28, Antonio Miller wrote: > We'll see if someone tears this argument apart, but you got me thinking... > > The propagation of sound in the atmosphere is pretty complicated [1], > but some simplified calculations might be relevant to this question. > > Attenuation of sound in Air at 100m [2]: > f<2kHz, less than 2dB > f=4kHz, 3dB > f=8kHz, 10dB > f=16kHz, 36dB > > A (very rough) calculation for a detection radius of a sound that is > 20dB above hearing threshold: > > 56m for 16kHz > 200m for 8kHz > 667m for 4kHz > > Meaning, you would have to be almost four times closer to the 16kHz > sound to detect it as the 8kHz sound. Assuming the 8 and 16kHz sound > are equally biologically relevant, I would tend to weight the > information content of the 16kHz sound much higher due to it's > relative spatial scarcity. Does that make sense to anyone? Maybe the > ability to hear higher frequency sounds helps lend a competitive > advantage because they only exist within short distances of the sound > source? > My guess would be that spatial scarcity is not as important as the fact that high frequency sounds are associated with events like twigs snapping, grass rustling, etc, which might indicate a nearby predator or prey. (I don't think predators emit low-frequency purring while they are stalking!) But now that you mention it, it might be very handy that these snaps and rustles have a limited range, since we don't want to get false positives from every leaf that falls in the forest! Best regards, Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!


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