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Matlab Code for Inverse Filtering

Below is the matlab source code used to extract the main Helmholtz air mode from the guitar body impulse response in Figures 8.14 through 8.17:

        freq = 104.98;  % estimated peak frequency in Hz
        bw = 10;        % peak bandwidth estimate in Hz

        R = exp( - pi * bw / fs);            % pole radius
        z = R * exp(j * 2 * pi * freq / fs); % pole itself
        B = [1, -(z + conj(z)), z * conj(z)] % numerator
        r = 0.9;     % zero/pole factor (notch isolation)
        A = B .* (r .^ [0 : length(B)-1]);   % denominator

        residual = filter(B,A,bodyIR); % apply inverse filter


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``Physical Audio Signal Processing'', by Julius O. Smith III, W3K Publishing, 2010, ISBN 978-0-9745607-2-4.
Copyright © 2014-06-11 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University
CCRMA