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1 function output = ERBFilterBank(x, fcoefs)
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2 % function output = ERBFilterBank(x, fcoefs)
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3 % Process an input waveform with a gammatone filter bank. This function
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4 % takes a single sound vector, and returns an array of filter outputs, one
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5 % channel per row.
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6 %
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7 % The fcoefs parameter, which completely specifies the Gammatone filterbank,
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8 % should be designed with the MakeERBFilters function. If it is omitted,
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9 % the filter coefficients are computed for you assuming a 22050Hz sampling
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10 % rate and 64 filters regularly spaced on an ERB scale from fs/2 down to 100Hz.
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11 %
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12
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13 % Malcolm Slaney @ Interval, June 11, 1998.
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14 % (c) 1998 Interval Research Corporation
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15 % Thanks to Alain de Cheveigne' for his suggestions and improvements.
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16
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17 if nargin < 1
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18 error('Syntax: output_array = ERBFilterBank(input_vector[, fcoefs]);');
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19 end
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20
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21 if nargin < 2
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22 fcoefs = MakeERBFilters(22050,64,100);
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23 end
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24
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25 if size(fcoefs,2) ~= 10
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26 error('fcoefs parameter passed to ERBFilterBank is the wrong size.');
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27 end
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28
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29 A0 = fcoefs(:,1);
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30 A11 = fcoefs(:,2);
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31 A12 = fcoefs(:,3);
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32 A13 = fcoefs(:,4);
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33 A14 = fcoefs(:,5);
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34 A2 = fcoefs(:,6);
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35 B0 = fcoefs(:,7);
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36 B1 = fcoefs(:,8);
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37 B2 = fcoefs(:,9);
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38 gain= fcoefs(:,10);
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39
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40 output = zeros(size(gain,1), length(x));
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41 for chan = 1: size(gain,1)
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42 y1=filter([A0(chan)/gain(chan) A11(chan)/gain(chan) ...
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43 A2(chan)/gain(chan)], ...
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44 [B0(chan) B1(chan) B2(chan)], x);
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45 y2=filter([A0(chan) A12(chan) A2(chan)], ...
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46 [B0(chan) B1(chan) B2(chan)], y1);
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47 y3=filter([A0(chan) A13(chan) A2(chan)], ...
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48 [B0(chan) B1(chan) B2(chan)], y2);
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49 y4=filter([A0(chan) A14(chan) A2(chan)], ...
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50 [B0(chan) B1(chan) B2(chan)], y3);
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51 output(chan, :) = y4;
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52 end
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53
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54 if 0
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55 semilogx((0:(length(x)-1))*(fs/length(x)),20*log10(abs(fft(output))));
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56 end
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