I have a Bosch cooker hood & in recent months there is an almost constant drumming noise coming from it when it's not in use. This only used to happen when it was windy outside but has not been the case recently. Any idea what might be causing it & how I can fix it please?

Tracey Hughes, August 2015

Check the anti-draft flaps in the outside vent aren't sticking open.

C, August 2015