They do buzz when you start them up. If that's what you are referring to, it's the nature of the beast. My A100 did it (gave to kid) and now the A500 does it.
Might be to differentiate whether the tablet is off or just "sleeping"
Don't start it up on a hard surface laying flat. You will hear it all over. Get a holder that will keep the noise to a minimum - It will still be noisy, but it won't be amplified.