The machine has been in operation for over a year now. But I haven't noticed any whirring in standby yet.

We now have the second Krups machine and both have a whirring noise in standby mode! So unfortunately the second machine is going back. Instead, we are ordering the DeLonghi again, which does not have this noise!

no buzzing here. but your socket may be incorrectly polarised. that could produce a buzz. the machine being switched off is more likely not.