different when dealing with a wave sound

[Stephen Zhang]

Hi, all
I have a wave sound here[1], which mixed a man's sound with some "beeee" sound. I tested this sound in matlab(windows version), octave(windows version) and octave(linux  version), but get diffenrent result. Details are here:

I use these commands:

[wav fs bps] = wavread('buzz.wav');

b = fir1(50, [X Y], 'bandpass');

y = filter(b, 1, wav);

wavwrite(y, fs, bps, 'test.wav');

When I set X=0.3, Y=0.7 (in line 2),In matlab and octave(windows version), I can clearly hear the man's sound saying "zhe li shi dian zi ke ji da xue"(Chinese) without any "beeee" sound while in octave(linux version), I can only hear "beeee" sound. Only when I set X=0.8 and Y=0.99 can I hear the man's sound(not very clearly) with "beeee" sound in octave's linux version.

I'd really like to know what causes difference? Is it a bug or just my fault?

Thanks a lot to read this email.

Regards,

Stephen

[1]http://pan.baidu.com/s/1dDtcTwt