请大侠看看错在哪里

comzrb

[x1,fs,bits]=wavread('eng.wav',[6000 65536]);
[x2,fs,bits]=wavread('out.wav',[6000 65536]);
[x3,fs,bits]=wavread('daish_01.wav',[6000 65536]);
[y,fs,bits]=wavread('drive.wav',[6000 65536]);
fs=6000;
nfft=65536;
window=boxcar(nfft/8);
noverlap=0;
p=1;
[Px1x1,Pxxc]=psd(x1,nfft,fs,window,noverlap,p);
[Pyy,Pxxc]=psd(y,nfft,fs,window,noverlap,p);
Px1y=csd(x1,y,nfft,fs,window,noverlap);
index=0:round(nfft/2-1);
k=index*fs/nfft;
plot_Px1y=10*log10(Px1y(index+1));
r1y2=(abs(Px1y)).^2/(Px1x1.*Pyy);
r1y=sqrt(r1y2);
figure(1)
plot(k,r1y(index+1));
??? Error using ==> mrdivide
Out of memory. Type HELP MEMORY for your options.



上面是对一组声音的分析，x1,x2,x3,y是声音文件在计算r1y2=(abs(Px1y)).^2/(Px1x1.*Pyy);时就会提示??? Error using ==> mrdivide
Out of memory. Type HELP MEMORY for your options.不计算它时就不会报错。小弟初学者，请大侠指导下。另外 ，想知道对求自谱互谱的参数有没有什么不对的   拜谢了