function [B,A] = cdsgn(Fs); % CDSGN  Design of a A-weighting filter.%    [B,A] = CDSGN(Fs) designs a digital A-weighting filter for %    sampling frequency Fs. Usage: Y = FILTER(B,A,X). %    Warning: Fs should normally be higher than 20 kHz. For example, %    Fs = 48000 yields a class 1-compliant filter.%%    Requires the Signal Processing Toolbox. %%    See also CSPEC, ADSGN, ASPEC. % Author: Christophe Couvreur, Faculte Polytechnique de Mons (Belgium)%         couvreur@thor.fpms.ac.be% Last modification: Aug. 20, 1997, 10:10am.% References: %    [1] IEC/CD 1672: Electroacoustics-Sound Level Meters, Nov. 1996. % Definition of analog C-weighting filter according to IEC/CD 1672.f1 = 20.598997; f4 = 12194.217;C1000 = 0.0619;pi = 3.14159265358979;NUMs = [ (2*pi*f4)^2*(10^(C1000/20)) 0 0 ];DENs = conv([1 +4*pi*f4 (2*pi*f4)^2],[1 +4*pi*f1 (2*pi*f1)^2]); % Use the bilinear transformation to get the digital filter. [B,A] = bilinear(NUMs,DENs,Fs);