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