This series of M-files generates A-weigthing, C-weighting, octave andone-third-octave digital filters. These filters are commonly used inacoustics, for example, in noise control.The implementation is based on the following standards: 	* IEC/CD 1672: Electroacoustics-Sound Level Meters, IEC, Geneva, Nov. 1996, 		for A- and C-weighting filters.	* ANSI S1.1-1986 (ASA 65-1986): Specifications for Octave-Band 	  and Fractional-Octave-Band Analog and Digital Filters, ASA, New York, 1993, 		for octave and one-third-octave filters. The following M-files are available:	octave.tar.gz 	Compressed Unix tar archive containing all of the files below.	README  	This file. 	adsgn.m		Design of a A-weighting filter.	aspec.m     	Plots a filter characteristics vs. A-weighting specifications.	cdsgn.m		Design of a A-weighting filter.	cspec.m     	Plots a filter characteristics vs. C-weighting specifications.	octdsgn.m   	Design of an octave filter.    	octspec.m   	Plots an octave filter characteristics.	oct3dsgn.m	Design of a one-third-octave filter.	oct3spec.m 	Plots a one-third-octave filter characteristics.	oct3bank.m  	Simple one-third-octave filter bank.   	filtbank.m    	One-third-octave band frequency analyser.        leq.m        	Computes the sequence of short-time RMS powers (Leq) of a signal.		bankdisp.m      Display filterbank power spectrum in 'bar' form.The M-files have been tested under MATLAB 4.1 and MATLAB 5.1. They should normally work under both versions of MATLAB if you disregard the warnings that might be issued in some cases. If it is necessary to make changes to a M-file to allow it to work with different versionsof MATLAB, just uncomment the adequate lines of code (alternate codeis provided in the M-file). -- Christophe Couvreur (couvreur@thor.fpms.ac.be), August 1997.  Sample utilisations of the M-files: ----------------------------------1) Conception of an A-weighting filter and verification of its characteristics:	>> Fs = 44100;	>> [B,A] = adsgn(Fs);	>> aspec(B,A,Fs); 2) Conception of a one-third-octave filter and verification of its characteristics:	>> Fs = 44100;	>> Fc = 4000; 	>> [B,A] = oct3dsgn(Fc,Fs);	>> oct3spec(B,A,Fs,Fc,'ansi'); 3) Construction of an octave or one-third-octave filter bank:	See the simple implementation (fixed sampling frequency) in OCT3BANK. 	Note that a multirate implementation is used to avoid problems	with the low frequency bands. 4) Analysis of a signal with FILTBANK: computation of time-varying A-weighted    one-third-octave Leq spectrum and display as a waterfall plot.    It is assumed that the signal is stored in the variable x.    The frame length for the analysis is T = 100ms.   	>> Fs = 48000;	>> T = 100e-3;	>> [B,A] = adsgn(Fs); 	>> x = filter(B,A,x); 	>> [P,F] = filtbank(x,Fs,T,'extended');	>> waterfall(P');	>> zlabel('Level [dB]');	>> ylabel('Frame #');	>> xlabel('Frequency band');	>> set(gca,'XTick',[2:3:length(F)]);	>> set(gca,'XTickLabel',F(2:3:length(F)));Contact & Comments: ------------------   Dr Ir Christophe Couvreur    Research Assistant, Belgian National Fund for Scientific Research   Department of Physics   Faculte Polytechnique de Mons                  Rue de Houdain 9                            Ph.  +32 65 374042   B-7000 Mons (Belgium)                       FAX  +32 65 374045   E-mail: Christophe.Couvreur@fpms.ac.be   WWW: http://thor.fpms.ac.be/~couvreur/