[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: High-frequency hearing in humans
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!