Another 172 buzzing noise

[len_beach]

When I have the ignition on listening to the stereo, the throttle actuator on the side of the inlet makes a buzzing noise.
Is this common and what is it doing?

 

[RobertCL]

I've noticed a similar thing. No idea if it is the throttle actuator, as I don't know what / where that is, but there is definitely a buzzing noise from under the bonet with the ignition on.

 

[ant]

yep, found that one today too