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Initial checkin for AIM92 aimR8.2 (last updated May 1997).
author | tomwalters |
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date | Fri, 20 May 2011 15:19:45 +0100 |
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.TH GENASA 1 "11 May 1995" .LP .SH NAME .LP genasa \- generate auditory spectral analysis .LP .SH SYNOPSIS .LP genasa [ option=value | -option ] [ filename ] .LP .LP .SH DESCRIPTION .LP The genasa module of the AIM software performs a time-domain spectral analysis on the input wave using a bank of auditory filters, and summarises the information in a sequence of auditory spectra. The spectral analysis converts the input wave into an array of filtered waves, one for each channel of a gammatone auditory filterbank. The surface of the array of filtered waves is AIM's representation of basilar membrane motion (BMM) as a function of time. The sequence of auditory spectra is produced by calculating the envelope of the BMM and extracting spectral slices from the envelope every 'frstep_epn' ms. The envelope is calculated continuously, by rectifing, compressing, and lowpass filtering the individual BMM waves as they flow from the filterbank. .LP The auditory spectrum produced by genasa is intended to simulate the spectral representation of a sound as it occurs in the peripheral auditory system just prior to neural transduction. As a result, the frequency resolution of the analysis varies with the center frequency of the channel, and the distribution of channels across frequency is chosen to match that in the auditory system. The auditory spectrum is a plot of the activity in each channel as a function of the centre frequency of the auditory filter (in ERB's). The representation is referred to as an auditory spectrum to distinguish it from the Fourier energy spectrum (Patterson, 1994a). The suffix 'asa' is short for 'auditory spectral analysis'; it is used to distinguish this spectral representation from three other spectral representations provided by the AIM software ('epn' excitation pattern, 'sgm' auditory spectrogram, and 'cgm' cochleogram). .LP The spectral analysis performed by genasa is the same as that performed by genbmm. The primary differences are in the display defaults and the inclusion of the Compression and Leaky Integration modules used to construct the spectral slices from the BMM. As a result, this manual entry is restricted to describing the option values that differ from those in genbmm and the additional options required to control the Compression and Leaky Integration. .LP .SH DISPLAY DEFAULTS .LP The default values for three of the display options are reset to produce a spectral format rather than a landscape; specifically, display=excitation, bottom=0 and top=2500. The number of channels is increased to 128 to ensure reasonable frequency resolution in the spectral display. .LP .SH COMPRESSION AND LEAKY INTEGRATION .LP Compression and lowpass filtering are activated and the neural encoding stage that comes between them is turned off: .LP .LP .SS "Compression" .PP Auditory spectra are usually produced via the functional route in AIM. In this case, compress is set on .LP .TP 13 compress Logarithmic compressor switch .RS Switch. Default: on. .RE .RS .LP Note: The compressor in the functional route of AIM is logarithmic and it screens out negative BMM values before compression. This rectifies the wave during the compression process and so the separate rectify option is left off. .RE .LP .RS .LP Note: The compressor in the physiological route of AIM is an integral part of the tlf module, so when using this route to produce auditory spectra, turn off the logarithmic compressor (i.e. compress=off). The compressor in tlf does not screen out negative values so it is also important to set rectify=on. .RE .RS .LP Full wave rectification is produced if rectify is set to 2. This is useful when calculating envelopes with genasa. .RE .LP .LP .SS "Transduction" .PP .LP .TP 13 transduction Neural transduction switch (at, meddis, off) .RS Switch. Default: off. .RE .LP .LP .SS "Leaky Integration" .PP .LP .TP 13 stages_idt Number of stages of lowpass filtering .RS Default unit: scalar. Default value: 2 .RE .TP 13 tup_idt The time constant for each filter stage .RS Default unit: ms. Default value: 8 ms. .RE .LP The Equivalent Rectandular Duration (ERD) of a two stage lowpass filter is about 1.6 times the time constant of each stage, or 12.8 ms in the current case. .TP 13 frstep_epn The time between successive spectral frames .RS Default unit: ms. Default value: 10 ms. .RE .LP With a frstep_epn of 10 ms, genasa will produce spectral frames at a rate of 100 per second. .LP .TP 13 downsample The time between successive spectral frames. .RS Default unit: ms. Default value: 10 ms. .RE .LP Downsample is simply another name for frstep_epn, provided to facilitate a different mode of thinking about time-series data. .RE .LP .SH FILES .LP .TP 13 .genasarc The options file for genasa. .LP .SH SEE ALSO .LP genbmm, gensgm .LP .SH BUGS .LP None currently known. .SH COPYRIGHT .LP Copyright (c) Applied Psychology Unit, Medical Research Council, 1995 .LP Permission to use, copy, modify, and distribute this software without fee is hereby granted for research purposes, provided that this copyright notice appears in all copies and in all supporting documentation, and that the software is not redistributed for any fee (except for a nominal shipping charge). Anyone wanting to incorporate all or part of this software in a commercial product must obtain a license from the Medical Research Council. .LP The MRC makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty. .LP THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .LP .SH ACKNOWLEDGEMENTS .LP The AIM software was developed for Unix workstations by John Holdsworth and Mike Allerhand of the MRC APU, under the direction of Roy Patterson. The physiological version of AIM was developed by Christian Giguere. The options handler is by Paul Manson. The revised SAI module is by Jay Datta. Michael Akeroyd extended the postscript facilites and developed the xreview routine for auditory image cartoons. .LP The project was supported by the MRC and grants from the U.K. Defense Research Agency, Farnborough (Research Contract 2239); the EEC Esprit BR Porgramme, Project ACTS (3207); and the U.K. Hearing Research Trust.