in the frequency domain waveform of an audio file, it is showing frequency range in spectrum upto 100 kHz. but i want the range upto 1 kHz . wht is the wrong in frequency range? please provide correct frequency range.

yfft=fft(y); % fft of original signal

f=-length(y)/2:length(y)/2-1;

k=20*log10(abs(yfft));

plot(f,k);

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/29922-why-your-question-is-not-urgent-or-an-emergency