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Re: High-frequency hearing in humans
Good points Jose and Kevin; a few cm is the distance between the ears
and it makes evolutionary sense to be able to resolve inter-aural delays
that are critical in source localization, separation and identification.
Piotr's initial list of obvious reasons for using high frequency information
listed pinna and ILD, but ITD cues were omitted -- presumably because
high-frequency sine waves give highly ambiguous ITD location cues.
This makes it easy to label ITDs as only useful at low frequencies. But
real-life sounds are rarely slow-onset sine waves. The auditory system
has access to channelized ITD data (think eg cross-correlogram) which
for most sounds (and especially their onsets) provide critical information
for all subsequent auditory tasks.
If proof was needed, consider those of us whose high-frequency hearing
has declined. While ease of communication at cocktail parties may have
limited survival value, I agree with Jose: our "cocktail party" processors
are the same as our inherited "jungle" processors, and we may owe the
ability to distinguish sss from zzz, or the fine nuances of a brass onset or
the realism of a cymbal crash and the 'spaciousness' of a recording (vs.
a lower fidelity recording of same) to ancestral evolutionary pressures.
On Thu, Feb 3, 2011 at 2:29 AM, Jose Ignacio Alcantara <jia10@xxxxxxxxx> wrote:
> Not wishing to get sidetracked, but given that 'evolutionary (psychology of
> hearing)' seems to have been implied as a possible reason for our
> high-frequency hearing, I think it's best to be clear about what this
> actually means, so that the 'tail doesn't wag the dog'. It does seem true
> that our auditory system seems especially well tuned to perceive speech
> events, and as such, it is tempting to assume that this is because both
> language and audition developed (evolved) together. Another (equally valid
> and perhaps more parsimonious) explanation, which has also been proposed,
> might be that audition came 'first' and that language has co-opted the
> existing system in such a way that it has taken advantage of whatever
> auditory processing limits there were/are (and possible speech production
> limits as well). The latter explanation would also explain the observed
> fine tuning for speech, but crucially, it would posit that we are good at
> perceiving those speech sounds that we happen to be good at discriminating
> (and producing).
> In other words, as Kevin suggests, our high-frequency hearing most certainly
> came about before Liza Minnelli had cause to expound:
> "It's Liza with a Z, Not Lisa with an S, 'Cause Lisa with an S Goes "sss"
> not "zzz"..."
> On 2 Feb 2011, at 21:47, Kevin Austin wrote:
> Perhaps the question could be reframed as, "What are the evolutionary
> advantages of perceiving wavelengths of 1.5 to 4 cm, over not perceiving
> these wavelengths?" I would imagine that the upper limit of human hearing
> was developed well in advance of having to distinguish "zoo" from "sue".
> In my mind's eye [sic], I see wavelength more so than frequency in sound
> transmission / perception.
> On 2011, Feb 2, at 2:14 PM, Piotr Majdak wrote:
> Dear list,
> thank you all for the many responses. Below I try to sort and summarize the
> Reasons why extended (>8 kHz) high-frequency hearing may be important
> (besides sound localization!) :
> Piotr Majdak wrote:
> Dear list,
> I'm looking for the reasons for the good high-frequency* hearing in humans.
> The reasons I have until now are actually the obvious ones:
> * Pinna localization cues
> * Interaural level cues (ILD, they actually start to work from around 2 kHz)
> What do you think: if there were no need for the ILD and pinna cues, would
> there be any other reasons?
> *) say, above 8 kHz
> Piotr Majdak
> Psychoacoustics and Experimental Audiology
> Acoustics Research Institute
> Austrian Academy of Sciences
> Wohllebengasse 12-14, 1040 Vienna, Austria
> Tel.: +43 1 51581-2511
> Fax: +43 1 51581-2530