Baby monitor keeps coming on when baby is not there

[pamperedbaby]

I'm currently downstairs with baby and the the baby monitor upstairs which is audio only keeps coming on and making crackling and hissing sounds, nobody else is at home.

YANBU to be quite spooked?
YABU there is a perfectly reasonable explanation, such as .....?

Could it be to do with next door and picking up a signal of someone using their phone.

Could it be the neighbours one interfering with yours?

I'm not sure, we do live in a semi but I think they are both at work.