It is common for mirrors/cabinets with shaver sockets to make a humming/buzzing sound, we can assure you this does not mean there is a fault with the item.
The humming/buzzing sound is a sign that power from the LED transformer is circulating around the shaver transformer, which can cause the shaver transformer to vibrate against the backbox, this is what creates the sound. Please note that the shaver socket will only be activated when something is plugged into it.
After testing in house, we have found that the humming noise may be louder should your item be installed onto plasterboard or stud walls. We can recommend that tightening the screws which hold the transformer in place or fitting a small, heatproof rubber pad between the shaver socket transformer and the backbox of the mirror can silence the humming/buzzing.
As this isn't deemed as a fault it would be the responsibility of the customer to make these changes.
If you require a any more information around this please contact customer services on 01977 522021 or e-mail us at firstname.lastname@example.org.
Pebble Grey Support Team