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Re: High frequency hearing



Dear List

I don't know if this is the paper that Lars refers to, but I am curious to have the auditory list's opinion on this topic. It's not clear to me whether the effects reported could be some artifact or if they're real. You can find the entire paper on-line, but here's the reference and the abstract. Any thoughts?

Oohashi, Tsutomu, Emi Nishina, Manabu Honda, Yoshiharu Yonekura, Yoshitaka Fuwamoto, Norie Kawai, Tadao Maekawa, Satoshi Nakamura, Hidenao Fukuyama, and Hiroshi Shibasaki.
Inaudible High-Frequency Sounds Affect Brain Activity: Hypersonic Effect. J. Neurophysiol. 83: 3548-3558, 2000.

Although it is generally accepted that humans cannot perceive sounds in the frequency range above 20 kHz, the question of
whether the existence of such "inaudible" high-frequency components may affect the acoustic perception of audible sounds remains unanswered. In this study, we used noninvasive physiological measurements of brain responses to provide evidence that sounds containing high-frequency components (HFCs) above the audible range significantly affect the brain activity of listeners. We used the gamelan music of Bali, which is extremely rich in HFCs with a nonstationary structure, as a natural sound source, dividing it into two components: an audible low-frequency component (LFC) below 22 kHz and an HFC above 22 kHz. Brain electrical activity and regional cerebral blood flow (rCBF) were measured as markers of neuronal activity while subjects were exposed to sounds with various combinations of LFCs and HFCs. None of the subjects recognized the HFC as sound when it was presented alone. Nevertheless, the power spectra of the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) recorded from the occipital region increased with statistical significance when the subjects were exposed to sound containing both an HFC and an LFC, compared with an otherwise identical sound from which the HFC was removed (i.e., LFC alone). In contrast, compared with the baseline, no enhancement of alpha-EEG was evident when either an HFC or an LFC was presented separately. Positron emission tomography measurements revealed that, when an HFC and an LFC were presented together, the rCBF in the brain stem and the left thalamus increased significantly compared with a sound lacking the HFC above 22 kHz but that was otherwise identical. Simultaneous EEG measurements showed that the power of occipital alpha-EEGs correlated significantly with the rCBF in the left thalamus. Psychological evaluation indicated that the subjects felt the sound containing an HFC to be more pleasant than the same sound lacking an HFC. These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the "hypersonic effect."





At 16:04 07/11/02 +0100, you wrote:
And yet we now have audio equipment with 96 kHz sampling - what a waste!

The only evidence I have seen - which as been forwarded by the '96 kHz'
proponents and audio manufacturers are some EEG measurements done on humans
exposed to ultrasound, using few subjects.  It is a rather indirect method
and I don't know if this has been published.

The results could be interesting, and like Bob points out the only
meaningful way would be to have the object move.  This could be done using
some kind of moving chair that would circle a small region within the
duration of one stimulus.

Regards,

Lars Bramsl°w

-----------------------------------------------------
Lars Bramsl°w
Ph.D., M.Sc.E.E.
Audiology

Oticon A/S
Strandvejen 58
DK - 2900 Hellerup

phone:  +45 39 13 85 42
fax:    +45 39 27 79 00

mailto:lab@oticon.dk
http://www.oticon.com
-----------------------------------------------------


-----Original Message-----
From: David Robinson [mailto:david@ROBINSON.ORG]
Sent: 5. november 2002 15:28
To: AUDITORY@LISTS.MCGILL.CA
Subject: High frequency hearing


I am trying to discover the limits of high frequency
hearing in the most sensitive human listeners.

The standard MAF curve(s) are of little use because
a) The data does not extend to very high frequencies
(i.e. it usually stops between 15 and 20 kHz), and
b) the data is based on median results.

Ideally, I would like real data to confirm the
anecdotal evidence that young and/or gifted listeners
can hear up to 25kHz (or beyond?). Equal loudness data
would be useful too, but the most useful information
would be an indication (very very roughly) of the % of
listeners of a particular age who can hear a particular
frequency at a particular amplitude.

Is there anything like this in the published
literature? I have looked several times, but everything
I find stops at 16kHz! Also, anything other than median
results seems very thin on the ground.

Thanks in anticipation of any help - any pointers would
be very greatfully received!

Cheers,
David.
http://www.David.Robinson.org/

P.S. I can't see the local primary school being too
keen to lend out children for a high frequency
listening test - is this the reason no one else has
studied this?

**NOTE**
Please use new e-mail address from now on:
robert.zatorre@mcgill.ca

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Robert J. Zatorre, Ph.D.
Montreal Neurological Institute
3801 University St.
Montreal, QC Canada H3A 2B4
phone: 1-514-398-8903
fax: 1-514-398-1338
web site: www.zlab.mcgill.ca