Buzzing

[AngloScot]

Why do electrical appliances eg TVs, Speakers, amplifiers, etc. make a buzzing noise and has it got anything to do with earth wires?:)

[dinsdale]

the electricity in the uk is ac. This means that the current flows positive and then negative (towards then away from your hi fi) in the UK this is at a rate of 50 cyles per minute or 50Hz (Hertz) this in turn can cause all elecrical eqipment to vibrate slightly (most noticable on equipment with speakers) or that is at high voltage as sound is caused by vibrations (hence the wind from speakers etc) your ears are able to pick up this vibration as the annoying buzzing sound you hear. the Higher the voltage (this pushes the current) the louder the sound, but its always the same frequency.

[dinsdale]

where i wrote 50 cycles per minute i meant to say per second (sorry)

[tomd]

The transformers (these convert from mains voltage to low voltages) in the equipment vibrate, AC current doesn't make the circuit boards themselves vibrate. However, most speakers don't have transformers in (only sometime the ones in supermarket ceilings) you shouldn't get any vibrations from home hifi speakers, although you may get a buzzing if you have an earth problem or a serverly cheap amp. AC current doesn't change the direction it flows in, the Neutral wire remains at 0v and the voltage of the Live wire alternates between +339 and -339v, giving an RMS (Root Mean Sqaured) value of 240v. At 50Hz though.

[Ray the DJ]

AC voltage creates a magnetic field that will interfere and influence any metal object or electrical device. Just having two components too close to each other or an AC cable next to a DC cable will cause interference, which, when amplified will cause a hum.