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1 function y=LyonPassiveEar(x,sr,df,earQ,stepfactor,differ,agcf,taufactor)
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2 % y=LyonPassiveEar(input, sample_rate, decimation, earQ, stepfactor);
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3 %
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4 % Changes
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5 % Zeroed out the preemphasis channels before doing the AGC. This is needed
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6 % so that cochlear inversion is possible (since we don't have those channels,
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7 % we can't invert their gain.)..... Malcolm 6/26/95
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8
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9 % (c) 1998 Interval Research Corporation
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10
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11 if nargin < 3
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12 fprintf('Syntax: y=LyonPassiveEar(input, sample_rate, decimation, earQ, stepfactor)\n');
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13 fprintf(' The input, sample_rate, and decimation parameters are mandatory.\n');
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14 return;
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15 end
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16
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17 if df < 1; df = 1; end
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18 if nargin < 4; earQ = 8; end
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19 if nargin < 5; stepfactor = earQ/32; end
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20 if nargin < 6; differ=1; end
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21 if nargin < 7; agcf=1; end
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22 if nargin < 8; taufactor=3; end
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23
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24 earFilters = DesignLyonFilters(sr, earQ, stepfactor);
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25
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26 nSamples = length(x);
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27 nOutputSamples = floor(nSamples/df);
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28 [nChannels filterWidth] = size(earFilters);
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29
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30 sosOutput = zeros(nChannels, df);
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31 sosState = zeros(nChannels, 2);
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32 agcState = zeros(nChannels, 4);
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33 y = zeros(nChannels, nOutputSamples);
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34
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35 decEps = EpsilonFromTauFS(df/sr*taufactor,sr);
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36 decState = zeros(nChannels, 2);
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37 decFilt = SetGain([0 0 1 -2*(1-decEps) (1-decEps)^2], 1, 0, sr);
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38
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39 eps1 = EpsilonFromTauFS(.64,sr);
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40 eps2 = EpsilonFromTauFS(.16,sr);
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41 eps3 = EpsilonFromTauFS(.04,sr);
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42 eps4 = EpsilonFromTauFS(.01,sr);
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43
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44 tar1 = .0032;
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45 tar2 = .0016;
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46 tar3 = .0008;
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47 tar4 = .0004;
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48
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49 if 0
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50 fprintf('df=%g, earq=%g, stepfactor=%g, differ=%g\n',df,earQ,stepfactor,differ);
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51 fprintf('agcf=%g, taufactor=%g\n', agcf, taufactor);
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52 [tar1 tar2 tar3 tar4; eps1 eps2 eps3 eps4]
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53 end
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54
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55 for i=0:nOutputSamples-1
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56 [sosOutput sosState]= soscascade(x(i*df+1:i*df+df), earFilters, ...
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57 sosState);
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58 output = max(0, sosOutput); %% Half Wave Rectify
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59 output(1) = 0; %% Test Hack to make inversion easier.
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60 output(2) = 0;
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61 if agcf > 0
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62 [output agcState] = agc(output, [tar1 tar2 tar3 tar4; ...
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63 eps1 eps2 eps3 eps4], ...
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64 agcState);
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65 end
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66
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67 if differ > 0
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68 output = [output(1,:);output(1:nChannels-1,:) - ...
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69 output(2:nChannels,:)];
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70 output = max(0, output);
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71 end
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72
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73 if df > 1
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74 [output decState] = sosfilters(output, decFilt, decState);
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75 end
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76 y(:,i+1) = output(:,df);
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77 end
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78
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79 %y = min(y,2*tar4);
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80 y=y(3:nChannels,:);
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