Making a clean notch in white noise signal?

[T_to_the_O]

Hi-

  I'm trying to find a good way to create a 1.5kHz notch in a white noise signal, but I'm having some difficulty.  I've attached the code below (in LV 8.5; it's a small piece of a much larger program), but basically I am using a random number generator to create the noise (at 44.1k samples/sec).  I then FFT to get to the frequency domain at which point I zero the frequencies that I want to notch out (as set by the "Lower" and "Higher Band Frequency" control). I then inverse transform the function back to the time domain and output it as an analog signal to the speaker.  The problem is that I'm not getting anything like a notch in the noise frequencies--at best, all frequencies are present or none are.

Any suggestionson how to get this piece of code to work? (Or a better way to do this...)

Thanks

[johnsold]

What makes you think the frequencies are not being removed?  If you graph the input to the Inverse FFT, it shows a nice stopband.

A random signal with a few frequency components removed is still a random signal, although it may no longer be white noise.

Lynn 

[seVEMes]

It looks like it worked to me. I posted the same code with graphs showing that it did work.