Humming noise under the stairs

[theprimeminister]

I have recently moved into a house (bulilt circa 1930) and have noticed a humming noise under the stairs, it seems louder if you disturb the cupboard (ie knock the wall getting the hoover out, slam the cupboard door etc)
The cupboard houses the gas meter, electric meter and the circuit breaker unit.
Is it normal to have these noises in an older house or is there an explanation?
I have switched off each section of the CBU and the main switch but the noise remains.
Thanks for your help.

 

[bernardgreen]

Old meters, the type with the spinning wheel. can hum even when there is no power being used. Ecomony 7 mechanical time switches may also hum. These are still powered even when the main switch is off.

Other possibilities are a door bell transformer connected to the consumer bus bar and not via a MCB though this should be depowered by the main switch being off,

If the wall is a thin party wall and next door's power supply is in the same place on the other side of the wall then the hum might be coming through the wall.

 

[pjcomp]

Is it a hum or more like a buzz? Sometimes a circuit breaker will develop a buzz (for a variety of reasons) and if so it's probably worth getting it changed, or at least checked out.

PJ