annotate man/man1/genasa.1 @ 0:5242703e91d3 tip

Initial checkin for AIM92 aimR8.2 (last updated May 1997).

.TH GENASA 1 "11 May 1995" 
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.SH NAME 
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genasa \- generate auditory spectral analysis 
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.SH SYNOPSIS 
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genasa [ option=value | -option ] [ filename ] 
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.SH DESCRIPTION 
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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.
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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).
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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.
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.SH DISPLAY DEFAULTS
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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.
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.SH COMPRESSION AND LEAKY INTEGRATION
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Compression and lowpass filtering are activated and the neural
encoding stage that comes between them is turned off:
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.SS "Compression"
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Auditory spectra are usually produced via the functional route in
AIM. In this case, compress is set on
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compress
Logarithmic compressor switch
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Switch. Default: on.
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.RS
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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. 
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.RS
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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.
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.RS
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Full wave rectification is produced if rectify is set to 2. This is
useful when calculating envelopes with genasa.
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.SS "Transduction"
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transduction
Neural transduction switch (at, meddis, off)
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Switch. Default: off.
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.SS "Leaky Integration"
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stages_idt
Number of stages of lowpass filtering
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Default unit: scalar. Default value: 2
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tup_idt
The time constant for each filter stage
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Default unit: ms. Default value: 8 ms.
.RE
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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.
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frstep_epn
The time between successive spectral frames
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Default unit: ms. Default value: 10 ms.
.RE
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With a frstep_epn of 10 ms, genasa will produce
spectral frames at a rate of 100 per second. 
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downsample
The time between successive spectral frames. 
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Default unit: ms. Default value: 10 ms.
.RE
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Downsample is simply another name for frstep_epn, provided to
facilitate a different mode of thinking about time-series data.
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.SH FILES
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 .genasarc 
The options file for genasa.
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.SH SEE ALSO
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genbmm, gensgm
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.SH BUGS
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None currently known.
.SH COPYRIGHT
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Copyright (c) Applied Psychology Unit, Medical Research Council, 1995
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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.
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The MRC makes no representations about the suitability of this 
software for any purpose.  It is provided "as is" without express or 
implied warranty.
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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.
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.SH ACKNOWLEDGEMENTS
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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.
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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.