Re: [AUDITORY] Scream spectrum

As has been remarked previously in this thread, speech in general has a lot of energy in the single-digit kHz range, so having good hearing sensitivity at those frequencies would be advantageous. Whether the vocal tract or the ear canal evolved to become optimized towards the other, or whether both evolved towards one another, or whether it was already optimized by coincidence, might be hard to prove. One could look at a range of animals that depend on vocal communication for survival and see if the relationship holds.

The photoreceptors in our eyes are sensitive to a frequency range where the sun emits the highest intensity of radiation, so there is a precedent for source and receiver to be adapted to each other (although the situation is slightly different in hearing).

On Wed, Feb 8, 2017 at 12:50 AM Matthew Winn <mwinn2@xxxxxx> wrote:

It’s tempting to draw a connection between the ~3 kHz resonance of the voice and the ~3 kHz resonance of the ear canal. There are two reasons why I am reluctant to think too much of this coincidence:

First, if we take the evolutionary point of view, I would guess that we should be more interested in the screams of *babies* than adults. And given the smaller size of babies’ vocal tracts, I would no longer expect their peak resonance to align with that of our ear canal.

Second, while the ear canal peak is prominent (enough that we audiologists need to compensate for it while fitting any hearing aid that occludes the canal), our system is chronically calibrated to it. Yes, there is a resonance, but the resonance is there to amplify that 2-5 kHz region for *all* sounds, so all broadband sounds should be equally affected. It is much more elegant in my opinion to frame perception as perception of *change* rather than perception of static spectral peaks; obviously this is not my own original idea. One of the more impressive experimenters in this line of work in the auditory sciences is Christian Stilp, whose work is described here: https://louisville.edu/psychology/stilp/lab/research

Given these thoughts, I am more likely to marvel at the pleasant coincidence of resonance frequencies, but with a healthy dose of “aw shucks” rather than a press release or quest to support a particular narrative.

Matt

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Matthew Winn, Au.D., Ph.D.
Assistant Professor
Dept. of Speech & Hearing Sciences
University of Washington

On Mon, Feb 6, 2017 at 12:56 PM, Huron, David <huron.1@xxxxxxx> wrote:

Dear collective wisdom,

I recall reading somewhere (long ago) that most human screams exhibit a spectral peak in the 3 kHz region (more broadly, 2-5 kHz) coinciding with the threshold dip due to the ear canal resonance. The implication is that screams are co-adapted to the most sensitive region of human hearing.

Can anyone point me to a suitable reference? Even literature reporting power spectrum data for human screams would be useful.

David Huron