view man/man1/gensgm.1 @ 0:5242703e91d3 tip

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

.TH GENSGM 1 "11 May 1995" 
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.SH NAME 
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gensgm \- generate auditory spectrogram 
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.SH SYNOPSIS 
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gensgm [ option=value | -option ] [ filename ] 
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.SH DESCRIPTION 
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The gensgm module of the AIM software performs a time-domain spectral
analysis using a bank of auditory filters, and summarises the
information in an auditory spectrogram, that is, a spectrogram with
auditory frequency resolution and temporal resolution, rather than the
fixed frequency and temporal resolution of traditional speech
preprocessors.  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 auditory spectrogram is a plot of a sequence of spectral
slices extracted from the envelope of the BMM 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 frequency resolution of the analysis varies with the center
frequency of the channel as in the auditory system, and the
distribution of channels across frequency is chosen to match that in
the auditory system (Patterson and Moore, 1986).  Thus, the auditory
spectrogram is a greyscale plot of the activity in each channel
(shades of black) as a function of time (the abscissa) and the centre
frequency of the auditory filter (the ordinate) in ERB's.  The
representation is referred to as an auditory spectrogram (SGM) to
distinguish it from more traditional spectrograms based on Fourier,
LPC or cepstral analysis. In AIM, the suffix 'sgm' is used to
distinguish this spectral representation from the other spectral
representations provided by the software ('asa' auditory spectral
analysis, 'cgm' cochleogram, and 'epn' excitation pattern).
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The spectral analysis performed by gensgm is the same as that
performed by genbmm (manaim genbmm). The primary differences are in
the display defaults and the inclusion of the Compression and Leaky
Integration modules used to produce the spectral slices that form the
spectrogram. 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 spectrographic format rather than a landscape. Specifically,
display=greyscale, bottom=0 and top=2500. The number of channels is
set to 128 for compatibility with the auditory spectrum modules,
genasa and genepn.  When using AIM as a preprocessor for speech
recognition the number of channels would typically be reduced to
between 24 and 32.  Use option 'downsample' if it is necessary to
reduce the output to less than 24 channels across the speech range.
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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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.TP 13
compress
Logarithmic compressor switch
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Switch. Default: on.
.RE
.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. 
.RE
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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.
.RE
.RS
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Full wave rectification is produced if rectify is set to 2. This
option value leads to smoother spectrograms. It is also useful when
calculating envelopes with genasa.
.RE
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.SS "Transduction"
.PP
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transduction
Neural transduction switch (at, meddis, off)
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Switch. Default: off.
.RE
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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, gensgm will produce spectral frames at a
rate of 100 per second.
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.TP 13
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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.TP 13
 .gensgmrc 
The options file for gensgm.
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.SH SEE ALSO
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genasa, genbmm, genepn, gencgm
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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.