view matlab/bmm/carfac/CARFAC_IHC_Step.m @ 593:40934f897a56

Fixed certain minor documentation bugs.
Added the CAR::designFilters and CAR::stageG methods. These methods design the CAR.coeff coefficients. They have been compared to be the same as the matlab coefficients.
An Ear is now contructed with a specific FS or, it uses the default.
Added the PsychoAcoustics class to do ERB and Hz conversions.
Added the EarTest.C main which allows the construction of an Ear class for testing.

% Copyright 2012, Google, Inc.
% Author: Richard F. Lyon
%
% This Matlab file is part of an implementation of Lyon's cochlear model:
% "Cascade of Asymmetric Resonators with Fast-Acting Compression"
% to supplement Lyon's upcoming book "Human and Machine Hearing"
%
% Licensed under the Apache License, Version 2.0 (the "License");
% you may not use this file except in compliance with the License.
% You may obtain a copy of the License at
%
%     http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS,
% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
% See the License for the specific language governing permissions and
% limitations under the License.

function [ihc_out, state] = CARFAC_IHC_Step(filters_out, coeffs, state);
% function [ihc_out, state] = CARFAC_IHC_Step(filters_out, coeffs, state);
%
% One sample-time update of inner-hair-cell (IHC) model, including the
% detection nonlinearity and one or two capacitor state variables.

% AC couple the filters_out, with 20 Hz corner
ac_diff = filters_out - state.ac_coupler;
state.ac_coupler = state.ac_coupler + coeffs.ac_coeff * ac_diff;

if coeffs.just_hwr
  ihc_out = min(2, max(0, ac_diff));  % limit it for stability
else
  conductance = CARFAC_Detect(ac_diff);  % rectifying nonlinearity

  if coeffs.one_cap;
    ihc_out = conductance .* state.cap_voltage;
    state.cap_voltage = state.cap_voltage - ihc_out .* coeffs.out_rate + ...
      (1 - state.cap_voltage) .* coeffs.in_rate;
  else
    % change to 2-cap version more like Meddis's:
    ihc_out = conductance .* state.cap2_voltage;
    state.cap1_voltage = state.cap1_voltage - ...
      (state.cap1_voltage - state.cap2_voltage) .* coeffs.out1_rate + ...
      (1 - state.cap1_voltage) .* coeffs.in1_rate;

    state.cap2_voltage = state.cap2_voltage - ihc_out .* coeffs.out2_rate + ...
      (state.cap1_voltage - state.cap2_voltage) .* coeffs.in2_rate;
  end

  % smooth it twice with LPF:

  ihc_out = ihc_out * coeffs.output_gain;
  state.lpf1_state = state.lpf1_state + coeffs.lpf_coeff * ...
    (ihc_out - state.lpf1_state);
  state.lpf2_state = state.lpf2_state + coeffs.lpf_coeff * ...
    (state.lpf1_state - state.lpf2_state);
  ihc_out = state.lpf2_state - coeffs.rest_output;
end

state.ihc_accum = state.ihc_accum + ihc_out;  % for where decimated output is useful