Zero Crossing Rate - optimize implementation

[jacek grabowski]

Hello,

I would like to ask You for any idea how to optimize following code:

s=wavread('sample.wav');
N=length(s)
framesize=2000;
frame_lim=[1:framesize:N-1];
FN=length(frame_lim);
zcr=zeros(1,FN-1);
tic()
for i=1:FN-1
    for k=frame_lim(1,i):frame_lim(1,i+1)
        if sign(s(k)) != sign (s(k+1))
         zcr(i)=zcr(i)+1;
        endif
    endfor
endfor
toc()

N =  236352
Elapsed time is 41.39265 seconds.

This is my first week with Octave, so forgive me any stupid question ... :)
Thank you very much.

-- 
Jacek Grabowski