That's normal - it's something to do with the ABS /TC system on start upAlso if I put my foot on the brake pedal before i start the engine you can feel it through the pedal when it makes that noise
From the replies, I would guess that is the case.
Another scary noise for you:
First time I dropped a wheel off a curb when accelerating and heard the whizzy chattering noise I thought wtf have I done - it's only the traction control system sorting stuff out (the ABS shuttle vale or some such) - it makes the same noise when the TC kicks in off road