Making a clean notch in white noise signal?


Making a clean notch in white noise signal?
  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...)
White Noise ‏19 KB
It looks like it worked to me. I posted the same code with graphs showing that it did work.
Vince M
Applications Engineer
White Noise ‏105 KB
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