asr.m

ADSP TOOLBOX: Version 2.0 and gui m-files

function [e1,e2] = asr(t,h1,h2,a,b,c)
%ASR	Envelope function for FM synthesized note.
%	[e1,e2] = asr(t,h1,h2,a,b,c)
%	t=time array or length of array if scalar.
%	a,b,c are times as a fraction < 1 (not <=1)
%	h1, h2 are fractions to which sound decays
%	e1,e2 are envelopes
%	Defaults: a=0.18, b=0.32,c=0.75,h1=0.7,h2=0.6


% ADSP Toolbox: Version 2.0 
% For use with "Analog and Digital Signal Processing", 2nd Ed.
% Published by PWS Publishing Co.
%
% Ashok Ambardar, EE Dept. MTU, Houghton, MI 49931, USA
% http://www.ee.mtu/faculty/akambard.html
% e-mail: [e-mail]
% Copyright (c) 1998



if nargin==0,help asr, t=0:0.001:3;x=cos(2*pi*30*t);[m1,m2]=asr(t);
sound(m1.*m2.*x);return,end



if nargin<6,c=0.75;end
if nargin<5,b=0.32;end
if nargin<4,a=0.18;end
if nargin<3,h2=0.6;end
if nargin<2,h1=0.7;end


l=length(t);if l==1,if t==round(t),l=t;end;end
na=fix(l*a);nb=fix(l*b);nc=fix(l*c);
n=0:l-1;
aa=1/na;bb=(1-h1)/(nb-na);cc=(h1-h2)/(nc-nb);dd=h2/(l-nc);
e1=aa*uramp(n)-(aa+bb)*uramp(n-na)+(bb-cc)*uramp(n-nb)+(cc-dd)*uramp(n-nc);
e2=aa*[uramp(n)-uramp(n-na)];