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Re: Bit-rate reduced audio and hearing loss


there was a MP3-Listening Test of the german c't-magazine
published in issue 6/2000
(http://www.heise.de/ct/00/06/092/default.shtml, in german).

The listener with the "best" differentiation between original
and coded signals turned out to be hearing impaired
(siginificant hearing loss above 8kHz).

However, I would not claim this test to be scientific relevant.


Lars Bramsl°w schrieb:
> Dear list,
> The modern audio compression techniques (MPEG, MP3, WMF etc..) can easily
> provide transparent audio quality if the bit-rate is sufficiently high, e.g.
> 256 kbit/s.  They are based on more or less advanced hearing models and
> exploit the temporal and spectral masking properties of the ear to keep all
> quantization errors below the masked thresholds.
> If these sounds are used with hearing impaired subjects and hearing aids,
> one could speculate that either the nature of the hearing loss or the
> hearing aid signal processing could potentially unmask the artefacts of the
> compression.  One such example would be a ski-slope hearing loss with normal
> LF hearing and severe HF hearing loss, combined with the appropriate
> frequency shaping, leading to audible artefacts in the normal hearing
> region.
> On the other hand, we can expect that the spectral and temporal resolution
> of the impaired ear is poorer than that of the normal ear.  So if the audio
> quality is transparent to the normal-hearing listener it will also be
> perceived as transparent by the hearing-impaired listener.
> Does anyone have good or bad experiences with hearing aid users and bit-rate
> reduced audio?
> Regards,
> Lars Bramsl°w

dipl. ing.
alexander lerch

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