[arnold19]

We have an 06 plate Cmax, and when the engine is off we occasionally get some very loud and strange noises (about once a month). They appear to come from the speakers, particularly the rear speakers, and sounds like a very large burst of static! - when it happens we can hear it from in the house, and it can sound like a firework display going off!

Any clues what it could be? Anyone else had this problem?

 

[RUSSBUS]

ONLY NOISE OURS MAKES AFTER LOCKING CAR IS WOT I THINK IS A RELAY CLICKING UNDER BONNET

 

[arnold19]

It definitely comes from the speakers, and is loud - we can hear from in the house as if someone is knocking to get out, but when you get close it sounds like a burst of static