Subject: Re: Bit-rate reduced audio and hearing loss From: alexander lerch <lerch(at)ZPLANE.DE> Date: Fri, 12 Jul 2002 13:33:44 +0200Hello, 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. Regards, Alexander Lars Bramsløw 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 Bramsløw -- dipl. ing. alexander lerch zplane.development http://www.zplane.de holsteinische str. 39-42 D-12161 berlin fon: +49.30.854 09 15.0 fax: +49.30.854 09 15.5