I had a shower fan installed about 8 months ago, a vent axia low carbon with timer on light switch. The separate small plastic box that contains all the wiring separate to the fan makes an electrical humming / buzzing sound, my electrician has said he can't hear it and didn't seem very concerned, he's very good and reliable normally.
But it's very audible in the silence of the bathroom when nothing else is on, it doesn't to buzz when the plastic front casing of the box wasn't fixed on and the wires were loose, it was like this for several weeks whilst wiring and partition ceiling was being finished. Surely the wires simply being pushed a little tighter into the box to fix on the front and close it shouldn't make it hum and buzz? What could this mean? Is it dangerous?