tomwalters@0: .TH GENBMM 1 "11 April 1994" tomwalters@0: .LP tomwalters@0: .SH NAME tomwalters@0: .LP tomwalters@0: genbmm \- generate basilar membrane motion tomwalters@0: .LP tomwalters@0: .SH SYNOPSIS tomwalters@0: .LP tomwalters@0: genbmm [ option=value | -option ] [ filename ] tomwalters@0: .LP tomwalters@0: .SH DESCRIPTION tomwalters@0: .LP tomwalters@0: The genbmm module of the AIM software simulates the spectral analysis tomwalters@0: performed by the auditory system using a bank of auditory filters. tomwalters@0: Specifically, genbmm converts an input wave into an array of filtered tomwalters@0: waves, one for each channel of the filterbank. The surface of the tomwalters@0: array of filtered waves is AIM's representation of basilar membrane tomwalters@0: motion (BMM) as a function of time. AIM provides two alternative tomwalters@0: methods for generating the BMM, linear, gammatone filterbank tomwalters@0: (Patterson et al, 1988; Slaney 1993, Cooke, 1993), or a nonlinear, tomwalters@0: transmission-line filterbank (Giguere and Woodland, 1994). For tomwalters@0: convenience, they are referred to as the 'functional' filterbank and tomwalters@0: the 'physiological' filterbank, respectively. tomwalters@0: .LP tomwalters@0: .SH OPTIONS tomwalters@0: .LP tomwalters@0: There are three sets of options for genbmm; they are grouped by tomwalters@0: function and identified by the suffixes _afb, _gtf and _tlf. The first tomwalters@0: set controls the distribution of the filtered waves across frequency tomwalters@0: (suffix _afb); the second specifies the shape of the gammatone filter tomwalters@0: (suffix _gtf); and the third specifies the shape of the transmission tomwalters@0: line filter (suffix _tlf). These three groups of options are the tomwalters@0: subject of this manual entry, together with an option that specifies tomwalters@0: the filter choice (gtf or tlf), and an option that specifies whether a tomwalters@0: middle ear function should be used with the gtf filterbank. tomwalters@0: .LP tomwalters@0: .SS "The Outer/Middle Ear function: middle_ear " tomwalters@0: .PP tomwalters@0: In the auditory system the middle ear causes a progressive attenuation tomwalters@0: of sound energy in the region below about 500 Hz and a progressive tomwalters@0: attenuation in the region above about 4000 Hz. There is also a tomwalters@0: primary auditory canal resonance around 2700 Hz that provides a boost tomwalters@0: in sound transmission. The resulting transfer function is a normal tomwalters@0: aspect of auditory processing and preceeds spectral analysis. If the tomwalters@0: functional filterbank is chosen (gtf), the outer/middle ear filter tomwalters@0: acts directly on the input wave, and the stapes velocity wave it tomwalters@0: generates is the input to the spectral filtering stage. If the tomwalters@0: physiological filterbank is chosen (tlf), the outer/middle ear and tomwalters@0: cochlear filter are performed simultaneously as in the auditory tomwalters@0: system. The only parameter associated with this function is the tomwalters@0: middle_ear switch which makes it possible to turn the outer/middle ear tomwalters@0: filtering off when the functional filterbank is chosen. tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: middle_ear tomwalters@0: Outer/middle ear switch tomwalters@0: .RS tomwalters@0: Switch. Default: on. tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: It is also possible to specify a floating point number, in which tomwalters@0: case the middle ear output is multiplied by that value. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Note: The middle_ear option is ignored if option filter (see below) tomwalters@0: is set to tlf. This is because the outer/middle stage and the tomwalters@0: cochlear stage are bidirectionally coupled in the transmission tomwalters@0: line filter implementation, and cannot be separated. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .SS "The Auditory FilterBank options: _afb " tomwalters@0: .PP tomwalters@0: The distribution of the filters across frequency and the total tomwalters@0: number of output filters in the bank are determined by four parameters: tomwalters@0: channels_afb, mincf_afb, maxcf_afb, and dencf_afb. tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: channels_afb tomwalters@0: The number of channels in the filterbank. tomwalters@0: .RS tomwalters@0: Default unit: filters. Default value: 75 tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: mincf_afb tomwalters@0: The minimum centre frequency tomwalters@0: .RS tomwalters@0: Default unit: Hz. Default value: 100 Hz. tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: maxcf_afb tomwalters@0: The maximum centre frequency tomwalters@0: .RS tomwalters@0: Default unit: Hz. Default value: 6000 Hz. tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: dencf_afb tomwalters@0: The density of the filters in the filterbank. tomwalters@0: .RS tomwalters@0: Units: filters/critical band. Default: off tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: dencf_afb provides an alternative method of specifying the number of channels tomwalters@0: in terms of the density of filters along the frequency scale. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Note: channels_afb overrides dencf_afb whenever it has a non-zero tomwalters@0: value. The values of dencf_afb and channels_afb may conflict at tomwalters@0: this point, in which case dencf_afb is ignored. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: WARNING: When using the transmission line filter (filter=tlf), the tomwalters@0: channel density should be 3 or more filters/erb. Using a lower tomwalters@0: density may lead to excessive spatial discretization errors (see tomwalters@0: Giguere and Woodland (1994) for a discussion). To view a small number tomwalters@0: of channels, use a reasonable density and reduce the number of tomwalters@0: displayed channels using option downchannel. tomwalters@0: .LP tomwalters@0: .TP 14 tomwalters@0: audiogram_afb tomwalters@0: The audiogram tomwalters@0: .RS tomwalters@0: Units: none. Default: off. Status: obsolete. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Note: In the versions up to and including AIM R6.15, this parameter tomwalters@0: was used as a means of approximating equal loudness contours, as well tomwalters@0: as middle ear attenuation. It applies a spectral weighting function at tomwalters@0: the output of the filterbank. With the addition of the outer/middle tomwalters@0: ear transfer function, this parameter is obsolete, and so the default tomwalters@0: value is off. Users who wish to use the audiogram parameter instead of tomwalters@0: the new outer/middle filter as a loudness equilisation function can tomwalters@0: still do so by setting audiogram_afb=on and middle_ear=off. As before, tomwalters@0: audiogram_afb is applied as a power function and so as the value of tomwalters@0: audiogram_afb decreases from 1 to 0, the degree of attenuation tomwalters@0: decreases. Values greater than unity are allowed but their tomwalters@0: interpretation is unclear. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The ERB scale for the gammatone auditory filterbank tomwalters@0: is specificed with three options: bwmin_afb, quality_afb, tomwalters@0: and mmerb_afb. tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: bwmin_afb tomwalters@0: The minimum bandwidth for an auditory filter. tomwalters@0: .RS tomwalters@0: Default unit: Hz. Default value: 24.7 tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: quality_afb tomwalters@0: The limiting quality factor for high frequency auditory filters. tomwalters@0: .RS tomwalters@0: Units: scalar. Default: 9.265 tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: mmerb_afb tomwalters@0: The length of one erb-rate unit along the basilar membrane. tomwalters@0: .RS tomwalters@0: Units: mm. Default: 0.89 tomwalters@0: .RE tomwalters@0: .LP 13 tomwalters@0: A listing of the parameters for the filter in the bank can be directed tomwalters@0: to the terminal at run time by setting info_afb=on. tomwalters@0: .RE tomwalters@0: .TP tomwalters@0: info_afb tomwalters@0: Print filterbank information to stderr. tomwalters@0: Switch. Default: off. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The physiological data on human cochlear frequency-position tomwalters@0: function (Greenwood, 1990) and the psychoacoustic data on auditory tomwalters@0: filter bandwidth (Patterson and Moore, 1986) indicate that the tomwalters@0: spectral analysis performed in the cochlea is like a 'constant Q' tomwalters@0: system (quality_afb) that asymptotes to a minimum filter bandwidth tomwalters@0: (bwmin_afb) at low centre frequencies. That is, tomwalters@0: .PD 0 tomwalters@0: .LP tomwalters@0: .PD 4 tomwalters@0: .LP tomwalters@0: erb = bwmin_afb + centre-frequency/quality_afb. tomwalters@0: .PD 0 tomwalters@0: .LP tomwalters@0: .PD 4 tomwalters@0: .LP tomwalters@0: If we assume, as Greenwood suggests, that each filter bandwidth tomwalters@0: corresponds to a constant distance (mmerb_afb) along the basilar tomwalters@0: membrane, it is possible to scale frequency in terms of erb units (or tomwalters@0: position along the basilar membrane) by integrating the inverse of the tomwalters@0: erb function above. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Glasberg and Moore (1990) have reviewed the available human filter tomwalters@0: shape data and concluded that the optimum values for bwmin_afb and tomwalters@0: quality_afb are 24.7 and 9.265, respectively, together with mmerb_afb tomwalters@0: of 0.89. (As a rule of thumb for rapid estimation, erb = 25 + 10% of tomwalters@0: cf ). The auditory scale used by Greenwood (1990) can be specified by tomwalters@0: setting bwmin_afb=22.85, quality_afb=7.238 and mmerb_afb=1.0. A tomwalters@0: reasonable approximation to the Bark scale (Zwicker, 1961) is obtained tomwalters@0: by setting bwmin_afb=80, quality_afb=6.5 and mmerb_afb=0.89. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .SS "Auditory filter design: filter " tomwalters@0: .PP tomwalters@0: The choice of filterbank -- linear gammatone or nonlinear transmission tomwalters@0: line -- is determined by option filter. tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: filter tomwalters@0: The auditory filter design tomwalters@0: .RS tomwalters@0: Default: gtf. Choices: gtf, tlf, off. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: When gtf is specified, the options below with suffix _gtf apply, and tomwalters@0: when tlf is specified, the options below with suffix _tlf apply. When tomwalters@0: off is specified, the input wave (or the stapes velocity) is passed on tomwalters@0: directly to the next stage. This provides for non-auditory use of the tomwalters@0: modules following the filterbank with their associated displays. For tomwalters@0: example, the envelope of the input wave (or stapes velocity) can be tomwalters@0: extracted using the rectification and integration modules that follow tomwalters@0: genbmm. The entry point genasa has the most convenient default tomwalters@0: settings for this purpose. The default value for the filter option is tomwalters@0: gtf. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .SS "The GammaTone Filter options: _gtf " tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: order_gtf tomwalters@0: The order of the gammatone filter tomwalters@0: .RS tomwalters@0: Units: none. Default: 4 tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: The order of the filter, order_gtf, determines the number of filtering tomwalters@0: stages and so it determines the slope of the skirts of the attenuation tomwalters@0: function and their extent. The default value is 4 and the range of tomwalters@0: useful values is from about 2 to 8. The processing time increases tomwalters@0: linearly with order above about order 2. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Note that the bandwidth calculation takes account of the fact that tomwalters@0: changes in order_gtf affect bandwidth. Thus, as long as bwmin_afb is tomwalters@0: fixed, changing the order will not affect the bandwidths of the tomwalters@0: resulting filters. Increasing the order of the filter increases the tomwalters@0: delay of the onset of the impulse response but it has little effect on tomwalters@0: the shape of the envelope of the impulse response for orders greater tomwalters@0: than three. The human auditory system is not sensitive to small phase tomwalters@0: changes between filter channels (Patterson, 1987) and so filter order tomwalters@0: is not well constrained by human experimental data. The default value tomwalters@0: (4) is used because this value provides the best match between the tomwalters@0: amplitude characteristics of the gammatone and roex filters for humans tomwalters@0: (Patterson et al., 1988). tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: gain_gtf tomwalters@0: Filter output amplification tomwalters@0: .RS tomwalters@0: Units: scalar. Default: 4. tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: The ratio of input to output level across the auditory filter tomwalters@0: when the input is a sinusoid at the cf of the filter. tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: phase_gtf tomwalters@0: The phase of the impulse response (obsolete) tomwalters@0: .RS tomwalters@0: Units: none. Default: 0. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: In the absence of phase compensation, the surface of basilar membrane tomwalters@0: motion has a strong rightward skew in the low-frequency channels tomwalters@0: because the filters get progressively narrower as centre frequency tomwalters@0: decreases, and this narrowing is accompanied by a slower filter tomwalters@0: response. There are occassionally non-auditory reasons for wanting to tomwalters@0: align the channels across frequency in one way or another. The tomwalters@0: software provides four alignment systems which are discussed at the tomwalters@0: end of this entry just before the references under the title Phase tomwalters@0: Alignment. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .SS "The Transmission Line Filter options: _tlf " tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: motion_tlf tomwalters@0: The basilar membrane output motion variable tomwalters@0: .RS tomwalters@0: Default: vel. Choices: vel, disp. tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: If vel (velocity) is specified, the output of genbmm tomwalters@0: is the basilar membrane velocity. If disp (displacement) tomwalters@0: is specified, the output of genbmm is the basilar membrane tomwalters@0: displacement. The default value is vel. tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: outdencf_tlf tomwalters@0: The density of the filters outside the display tomwalters@0: range. tomwalters@0: .RS tomwalters@0: Units: filters/critical band. Default: 4. tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: In the transmission line filter implementation, it is necessary to tomwalters@0: simulate the basilar membrane over its entire length. The option tomwalters@0: outdencf_tlf provides a means of specifying the number of additional tomwalters@0: channels that must be computed at the basal and apical ends of the tomwalters@0: cochlea, ie. outside the range specified by mincf_afb and maxcf_afb tomwalters@0: (see above). These additional channels are only computed for internal tomwalters@0: use and are not passed to the next stage of processing. tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: qref_tlf tomwalters@0: The local quality factor of each basilar membrane channel tomwalters@0: .RS tomwalters@0: Units: scalar. Default: 2. tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: Note: With the transmission line filter, the bandwidth is not tomwalters@0: determined by options bwmin_afb and quality_afb at high levels but tomwalters@0: rather by option qref_tlf (see above). tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: feedback_tlf tomwalters@0: The feedback gain of the outer hair cell circuit tomwalters@0: .RS tomwalters@0: Units: scalar. Default: 0.99 tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: WARNING: A value for feedback_afb greater than or equal to 1.0 can tomwalters@0: lead to unstable behaviour at low-levels (ie. oscillation). However, tomwalters@0: the model output will not grow unbound. The growth of the oscillations tomwalters@0: will be limited by the saturating nonlinearity of the outer hair cell tomwalters@0: circuit, and the model output will go into a kind of limit-cycle. tomwalters@0: These model oscillations have not yet been studied in detail and are tomwalters@0: likely to deviate substantially from real cochlear emissions. tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: dsat_tlf tomwalters@0: The basilar membrane displacement at the half-saturation point tomwalters@0: of the outer hair cell circuit tomwalters@0: .RS tomwalters@0: Units: cm. Default: 5.75e-6 tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: gain_tlf tomwalters@0: Filter output amplification tomwalters@0: .RS tomwalters@0: Units: scalar. Default: 4. tomwalters@0: .RE tomwalters@0: .RS tomwalters@0: .LP tomwalters@0: Note: There is an internal gain of 4.0 within the software of tomwalters@0: the transmission line model itself. The total gain is therefore tomwalters@0: 4.0 times the value for gain_tlf. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Note: A linearized version of the transmission line filter with tomwalters@0: roughly the same bandwidth as the gammatone filter can be obtained by tomwalters@0: setting feedback_tlf=0 and qref_tlf to about 10. The main difference tomwalters@0: is that the low-frequency skirt of the transmission line filter is tomwalters@0: less steep than that of the gammatone. tomwalters@0: .LP tomwalters@0: .SH FURTHER DESCRIPTION tomwalters@0: .LP tomwalters@0: .SS "The distribution of filter centres along the ERB scale. " tomwalters@0: .LP tomwalters@0: Given values for mincf_afb maxcf_afb and channels_afb (or tomwalters@0: dencf_afb), the program creates an array of centre frequencies tomwalters@0: in three steps: tomwalters@0: .LP tomwalters@0: 1. It centres a filter at 1.0 kHz. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: 2. Then it centres filters below 1.0 kHz, one after another, tomwalters@0: until it encounters mincf_afb. (Thus, mincf_afb is actually the tomwalters@0: frequency below which no filters are centred). The step size, tomwalters@0: that is the distance between centre frequencies, is determined tomwalters@0: by dencf_afb. When dencf_afb is equal to one, the centre tomwalters@0: frequencies are 1 ERB apart. The ERB is the Equivalent tomwalters@0: Rectangular Bandwidth of the filter (about 14% larger than the 3 tomwalters@0: dB bandwidth of the filter). The function relating the ERB to the tomwalters@0: centre frequency of the filter is taken from a `critical band' tomwalters@0: equation introduced by Greenwood (1961) and adapted to human tomwalters@0: auditory masking by Glasberg and Moore (1990). tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: 3. Finally, the program centres filters one after another in tomwalters@0: the region above 1 kHz until it encounters maxcf_afb (which is, tomwalters@0: actually, the frequency above which no filters are centred). When tomwalters@0: dencf_afb is increased, say to two, the program allocates two tomwalters@0: filters per critical band and spaces them at half ERB steps. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Note: It is not the bandwidths of the filters that are tomwalters@0: controlled by dencf_afb but rather the density of filters along tomwalters@0: the frequency axis. Thus, doubling dencf_afb does not cause the tomwalters@0: bandwidth of the filters to be halved; rather it results in more tomwalters@0: overlap between adjacent filters. With regard to the images tomwalters@0: produced by genbmm, dencf_afb determines the density of lines on tomwalters@0: the surface rather than the shape of the features that appear on tomwalters@0: the surface. tomwalters@0: .LP tomwalters@0: .SH MOTIVATION tomwalters@0: .LP tomwalters@0: The motivation for adopting the gammatone filter shape is tomwalters@0: threefold: tomwalters@0: .LP tomwalters@0: 1. It provides an excellent summary of physiological data tomwalters@0: concerning the impulse response of primary auditory neurons in tomwalters@0: small mammals such as cats (de Boer and de Jongh, 1978; Carney and tomwalters@0: Yin, 1989) tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: 2. The amplitude characteristic of the gammatone filter is very tomwalters@0: similar to that of the Roex filter commonly used to represent the tomwalters@0: human auditory filter (Patterson, et al, 1982; Schofield, 1985; tomwalters@0: Patterson et al, 1988) . tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: 3. There are recursive gammatone filters that make the calculation tomwalters@0: particularly fast both on general purpose computers and special tomwalters@0: purpose DSP chips (Holdsworth et al, 1988; Cooke, 1993; Slaney, 1993). tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: In summary, the gammatone filter is designed to provide a reasonable tomwalters@0: trade-off between accuracy in simulating basilar membrane motion, and tomwalters@0: computational load. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The motivation for adopting the transmission line filter is tomwalters@0: as follows: tomwalters@0: .LP tomwalters@0: 1. The outer hair cell circuit of the transmission line filter is tomwalters@0: level dependent and so this design produces level-dependent basilar tomwalters@0: membrane tuning curves (Giguere and Woodland, 1994). There is now tomwalters@0: ample evidence that the basilar membrane motion is indeed highly tomwalters@0: nonlinear and a major source of level compression (eg. Johnstone et tomwalters@0: al., 1986). tomwalters@0: .LP tomwalters@0: 2. The internal structure of the transmission line filter model is tomwalters@0: based on the physics of the auditory periphery and therefore provides tomwalters@0: a more realistic cochlear simulation than parallel filterbanks. It tomwalters@0: generates combination tones of the form 2f1-f2 as observed in the tomwalters@0: auditory system and it has the potential to generate cochlear echoes. tomwalters@0: .LP tomwalters@0: 3. The wave-digital-filter implementation of the transmission line tomwalters@0: filterbank is only about twice as slow as the gammatone filterbank tomwalters@0: for an equivalent number of channels. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .SH "Phase Alignment" tomwalters@0: .LP tomwalters@0: There is no question that the output of the cochlea has a phase lag tomwalters@0: corresponding to the strong rightward skew. However, perceptual tomwalters@0: evidence indicates that this phase lag has to be enormous (> 4ms) to tomwalters@0: affect what we hear; indeed, reversing the phase lag with synthetic tomwalters@0: stimuli does not change what we hear (Patterson, 1987). Phase tomwalters@0: information that appears in the basilar membrane motion but which we tomwalters@0: do not hear, is removed in the third module by the strobe mechanism of tomwalters@0: the temporal integration process. As a result, the stabilised auditory tomwalters@0: images are always phase aligned even though the basilar membrane tomwalters@0: motion and the neural activity patterns are not. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Prior to discovering the integration mechanism, we wanted to find tomwalters@0: a way of reducing the skew from the basilar membrane image, in tomwalters@0: order to provide a visual representation that was more like what tomwalters@0: we hear. The genbmm program provides the following options for tomwalters@0: phase aligning the responses of successive filters, determined tomwalters@0: by the value of the option phase_gtf: tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Value Effect tomwalters@0: .PP tomwalters@0: .TP 7 tomwalters@0: -1 tomwalters@0: Envelope alignment. tomwalters@0: .RS tomwalters@0: Shift the channels of output horizontally so that the points of tomwalters@0: maximum response to an impulse (ie the envelope maxima) will be aligned. tomwalters@0: .RE tomwalters@0: .TP 7 tomwalters@0: -2 tomwalters@0: Envelope plus fine structure alignment. tomwalters@0: .RS tomwalters@0: Perform envelope-peak alignment as in option -1 and then shift the tomwalters@0: fine structure phase in each channel so that a fine- structure peak tomwalters@0: coincides with the envelope peak. tomwalters@0: .RE tomwalters@0: .TP 7 tomwalters@0: -4 tomwalters@0: Envelope plus peak alignment, `left justified'. tomwalters@0: .RS tomwalters@0: Align the envelopes and fine structure of all of the impulse responses tomwalters@0: along the left edge of the image. tomwalters@0: .RE tomwalters@0: .TP 6 tomwalters@0: 0 tomwalters@0: No phase compensation. tomwalters@0: .TP 7 tomwalters@0: +n tomwalters@0: Advance each channel by n cycles of the centre frequency of the channel. tomwalters@0: Approximate envelope alignment is achieved using phase_gtf = 3 tomwalters@0: or 4. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: We experimented with a number of phase compensation schemes tomwalters@0: (Patterson et al., 1989) and concluded that the best option was tomwalters@0: envelope plus peak alignment which corresponds to a value of tomwalters@0: phase_gtf = -4. Accordingly, we recommend the use of phase_gtf tomwalters@0: values of 0 (ie no phase compensation) or -4 (envelope plus peak tomwalters@0: alignment). The remaining options are occasionally useful and so tomwalters@0: they have been left in the software. tomwalters@0: Note that for any phase compensation option other than 0 the time tomwalters@0: scale is strictly correct only for the lowest channel. For any tomwalters@0: other channel, the origin of the abscissa is offset to the right tomwalters@0: by an amount equal to the difference between `the envelope peak tomwalters@0: time of the lowest-frequency channel' and `the envelope peak time tomwalters@0: of the given channel'. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .SH REFERENCES tomwalters@0: .LP tomwalters@0: .RE tomwalters@0: .TP 4 tomwalters@0: de Boer, E., and de Jongh, H.R. (1978). On cochlear encoding: tomwalters@0: potentialities and limitations of the reverse-correlation tomwalters@0: technique, J. Acoust. Soc. Am., 63, 115-135. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Carney, L.H. and Yin, C.T. (1988) 'Temporal coding of resonances tomwalters@0: by low-frequency auditory nerve fibers: Single fibre responses tomwalters@0: and a population model', J.Neurophysiology, 60, 1653-1677. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Cooke, M.P. (1993). Modelling Auditory Processing and tomwalters@0: Organisation, Cambridge University Press. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Giguere, C. and Woodland, P.C. (1994). A computational model of tomwalters@0: the auditory periphery for speech and hearing research. I. Ascending tomwalters@0: path. J.Acoust. Soc. Am. 95: 331-342. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Glasberg, B.R. and B.C.J. Moore (1990). Derivation of auditory tomwalters@0: filter shapes from notched-noise data. Hearing Research, 47, tomwalters@0: 103-138. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Greenwood, D.D. (1961) 'Critical bandwidth and the frequency tomwalters@0: coordinates of the basilar membrane', J. Acoust. Soc. Am. 33, tomwalters@0: 1344-1356. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Greenwood, D.D. (1990). A cochlear frequency-position function tomwalters@0: for several species - 29 years later. J. Acoust. Soc. Am., 87, tomwalters@0: 2592-2605. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Holdsworth, J., Nimmo-Smith, I., Patterson, R.D. and Rice, P. tomwalters@0: (1988) Annex C of 'Spiral Vos Final Report, Part A: The tomwalters@0: Auditory Filterbank,' APU report 2341. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Johnstone, B.M. et al. (1986). Hear Res. 22: 147-153. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Moore, B.C.J and Glasberg, B.R. (1983), "Suggested formulae for tomwalters@0: calculating auditory filter bandwidths and excitiation patterns," tomwalters@0: J. Acoust. Soc. Am. 74, pp 750-753. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Patuzzi, R., and Robertson, D. (1988) "Tuning in the mammalian tomwalters@0: cochlea," Physiological Reviews 68, 1009-1082. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Patterson, R.D. (1976). Auditory filter shapes derived with tomwalters@0: noise stimuli. J. Acoust. Soc. Am., 59, 640-654. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Patterson, R.D. (1987). A pulse ribbon model of monaural phase tomwalters@0: perception. J. Acoust. Soc. Am., 82, 1560-1586. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Patterson, R.D., Nimmo-Smith, I., Weber, D.L., and Milroy, R. tomwalters@0: (1982). The deterioration of hearing with age: Frequency tomwalters@0: selectivity, the critical ratio, the audiogram, and speech tomwalters@0: threshold. J. Acoust. Soc. Am., 72, 1788-1803. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Patterson, R.D., Allerhand, M.H. and Holdsworth, J. (1992) tomwalters@0: 'Auditory representations of speech sounds', In Visual tomwalters@0: representations of speech signals, Eds. Martin Cooke and Steve tomwalters@0: Beet, John Wiley & Sons. 307-314. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Patterson, R. D., Holdsworth, J., Nimmo-Smith, I., and Rice, P. tomwalters@0: (1988). SVOS Final Report: The Auditory Filterbank. APU report 2341. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Patterson, R.D. and B.C.J. Moore (1986). Auditory filters and tomwalters@0: excitation patterns as representations of frequency tomwalters@0: resolution. In: Frequency Selectivity in Hearing (B. C. J. tomwalters@0: Moore, ed.), pp. 123-177. Academic Press, London. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Schofield, D. (1985) 'Visualisations of speech based on a model tomwalters@0: of the peripheral auditory system', NPL Report DITC 62/85. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Slaney, M. (1993) An efficient implementation of the Patterson- tomwalters@0: Holdsworth auditory filter bank. Apple Computer Technical tomwalters@0: Report #35. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .TP 4 tomwalters@0: Zwicker, E. (1961) Subdivision of the audible frequency range into tomwalters@0: critical bands (frequenzgruppen). J. Acoust. Soc. Am. 33, 248. tomwalters@0: .LP tomwalters@0: .SH EXAMPLES tomwalters@0: .LP tomwalters@0: The following command generates basilar membrane motion using the tomwalters@0: gammatone filter design (the default) for an input filename cegc: tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: example% genbmm cegc tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The following command generates basilar membrane motion using the tomwalters@0: gammatone filter design (the default) for a filterbank with cf from tomwalters@0: 200 Hz to 5000 Hz at a density of 4 filters/critical band for the same tomwalters@0: input filename: tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: example% genbmm channels=0 mincf=200 maxcf=5000 dencf=4. cegc tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The following command generates basilar membrane motion using the tomwalters@0: gammatone filter design (the default) and the audiogram function tomwalters@0: instead of the outer/middle ear filter: tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: example% genbmm middle_ear=off audiogram=on cegc tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The following command generates the basilar membrane motion using the tomwalters@0: transmission line filter design instead of the default gammatone tomwalters@0: filter: tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: example% genbmm filter=tlf cegc tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The following command generates the basilar membrane motion using the tomwalters@0: transmission line filter design and the auditory scale of Greenwood tomwalters@0: (1990): tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: example% genbmm filter=tlf bwmin=22.85 quality=7.238 mmerb=1.0 cegc tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The following command generates the basilar membrane motion using the tomwalters@0: transmission line filter design, but with the nonlinear outer hair tomwalters@0: cell feedback mechanism turned off: tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: example% genbmm filter=tlf feedback=off cegc tomwalters@0: .LP tomwalters@0: .SH FILES tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: .genbmmrc tomwalters@0: The options file for genbmm. tomwalters@0: .LP tomwalters@0: .SH SEE ALSO tomwalters@0: .LP tomwalters@0: genasa, gensgm tomwalters@0: .LP tomwalters@0: .SH BUGS tomwalters@0: .LP tomwalters@0: There is a bug in the hiddenline plotting of genbmm. It shows up when tomwalters@0: the surface has deep valleys and there is a large phase delay. The tomwalters@0: negative peaks show through on surfaces where they should be hidden. 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. tomwalters@0: