gendtmf.m

用matlab仿真产生双音多频DTMF信号.

%function [wav]=genDTMF(telnum)
%Usage:
%[wav]=genDTMF(telnum)
%For example:
function wav=genDTMF([2 6 5 3 6 1 9 8]);

%the elaspe time of a dial
elapse_time=0.04;

%sampling frequency
Fs  = 8000;
%the time sequence of a dial
t   = (0:elapse_time*Fs)/Fs;
pit = 2*pi*t;

%DTMF look up table
fc = [697 770 852 941];
fr = [1209 1336 1477]; 
f  = [];
for c=1:4,
	for r=1:3,
		f = [ f [fc(c);fr(r)] ];
		end
end
    
%generate the tones for 12 dial numbers
for i=1:size(f,2),
	tones(:,i) = sum(sin(f(:,i)*pit))';
end

%determine how many numbers dialed
len=length(telnum);
%generate the seed for random
rand('seed',telnum(1));

%generate the silent tone before dialing
wav=zeros(1,round(rand*100));
for i=1:len
   if telnum(i)==0
      telnum(i)=11; % the number '0' is in the 11th position
   end
   %generate tone of each dial number with a sequence of silent tone
   wav=[wav tones(:,telnum(i))' zeros(1,round(rand*6000+1000))];
end

%the whole tone is disturbed with a small noise
wav=wav+rand(1,length(wav))/50;

%play this tone
wavplay(wav,Fs);

%plot it.
plot((1:length(wav))/Fs,wav)