Bit-rate reduced audio and hearing loss (=?iso-8859-1?Q?Lars_Bramsl=F8w?= )


Subject: Bit-rate reduced audio and hearing loss
From:    =?iso-8859-1?Q?Lars_Bramsl=F8w?=  <LAB(at)OTICON.DK>
Date:    Fri, 12 Jul 2002 12:53:17 +0200

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 ----------------------------------------------------- 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(at)oticon.dk http://www.oticon.com -----------------------------------------------------


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