It's like a really really loud white noise that will last a few seconds before it stops... or before I turn off and back on the reverb.
Besides that, both FX work really fine together! But I'm really scared to have a heart attack at 4:00am in the morning, when is quiet everywhere, with my headphones on, and suddenly... SSSSSSSSSSSSSSSSSSSSSSSS!!!!
Edit: forgot to attach the machine details:
Sony Vaio - Intel Core 2 Duo T5600 @ 1.83 GHz / 2 GB RAM / WinXP Pro