I have not seen this problem in anyone elses car, but other people have posted, in this thread, that they have similar sounds, be it not as load.
To describe how loud my noise is; I have a bocsh 044 external fuel pump mounted in my boot, near the battery. These pumps are bloody loud, especially with the windows closed, on idle. The sound was just as loud, and that's with the windows closed! Only happened twice or three times.
I've had the Excedy twin plate for approx 11 months and the noise only started about a month ago. The clutch is definately not worn.
If the take-up point is too low to the floor, the clutch MAY not be disengaging properly.