From: rubaea!lehnert (Hilmar Lehnert) Subject: Re: What is the resolution of human hearing Date: Fri, 19 Jul 91 10:48:06 MET DST Re : What is the resolution of human hearing? Hi everybody, Since the question arised, I will try to give some data on the human auditory system. These are mainly 'best values' and might be used as a worst-case considerations for system designers. I posted part of this stuff some weeks before and I apologize repeating me. Frequency range : 16 Hz - 20 kHz Performance is not very well at the high and the low frequency edge. The roll of at the high end is quite sharp (and for most of adult people at a lower frequency then 20 kHz). The low edge is not easy to measure because other sensory modalities get involved. The highest sensitivity is around 3 kHz, where it is close to the physical limit (thermal noise of air). Frequency resolution : better the 1 Hz at 1 kHz Depends strongly on the kind of signals used for measurements. Temporal properties and phase sensitivity : >From the high frequency edge one can easily determine the required sampling frequency to maintain all audible information (> 40 kHz). Presenting two signals with a delay causes quite different effects depending on the kind of signals and the delay. This can be changings in timbre, in the localization and also distinct echos. The human ear is not very sensitive to monaural phase shifts (same phase shift at both ears or one ear switched off completely). But interaural phase shifts causes effects on the localization and the ear can sense interaural delays of less the 10 micro seconds (!!). Dynamic range : 120 dB The upper limit is determined at the point where it starts to hurt and the lower by the hearing threshold. However, there are some people, that can take some dB's more but exposing yourself to that levels will significantly lift your hearing threshold by permanently damaging your hearing and the overall dynamic range will decrease. Due to so-called masking effects a signal-to-noise ratio of about 85 dB will do for almost every application. Dynamik resolution : ca. 1 dB Sereo amplifiers with fixed steps at the volume control usually use steps of approx. 3 dB (each step doubles the energy). Coverage : full sphere (360x180) Spatial resolution : The human auditory system is full 3D, and so I use spherical coordinates here. Azimuth : better then 1 degree Elevation : better then 10 degrees Distance : better then 0.5 m has been reported, but still under investigation These data has been measured with no head movements allowed. It is possible that (especially the elevation resolution) will get better if dynamic effects are included. Special Features : - Can't be switched off - Complex pattern recognition for perception of localization - Inverse directional filtering for perception of timbre - Hardware spectrum analyzer (cochlea) - Noise reduction and reverberation suppression by binaural processing (cocktail party effect) - Main input channel for communication (speech recognition) - and many many more Hilmar (Hilmar Lehnert lehnert@aea.e-technik.uni-bochum.de)