transmission noise?

[drunken monkey]

my sisters KA has a tendency to make a strange noise at first gear when moving off from stationary.
it happens as you brign the clutch up and coincides with the car beginning to move. As you bring the clutch up and add gas, it stops.

it sounds like it's coming from possibly the gearbox or clutch but i am in no way techically savvy enough to be able to identify it by ear.
It only ever seems to happen on the road and attempts to replicate it at the garage whenever it goes in for a service have always failed.

anyone have similar experience?
any ideas/help?

thanks.