程序源代码如下: %t=0.001:0.001:1; t=1:1000; s1=sin(2*pi*50*t*0.001)+sin(2*pi*120*t*0.001)+rand(1,length(t)); for t=1:500; s2(t)=sin(2*pi*50*t*0.001)+sin(2*pi*120*t*0.001)+rand(1,length(t)); end for t=501:1000; s2(t)=sin(2*pi*200*t*0.001)+sin(2*pi*120*t*0.001)+rand(1,len ...