Just turn off all voices and turn on the noise voice. You can even use the built-in filter or use the master volume on it to make it fade in or fade out.
turn off all oscillators except for the noise oscillator, automate the lowpass filter on the pulv to sweep from 18 hZ (or whatever the minimum setting is) to the highest setting. adjust the resonance setting (located near the filter cutoff control) to taste.
Just turn off all voices and turn on the noise voice. You can even use the built-in filter or use the master volume on it to make it fade in or fade out.