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Bit-rate reduced audio and hearing loss

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

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?


Lars Bramsl°w

Lars Bramsl°w
Ph.D., M.Sc.E.E.

Oticon A/S
Strandvejen 58
DK - 2900 Hellerup

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