We starting hearing a popping noise when we flicked the switch in our bedroom. Then we started hearing it on the same wall but a switch in the hallway. We had an electrician come to change the switches.
He put in brand new switches however, we are still hearing the popping noise. Now it has traveled down the hallway to the bathroom light switch.
Once, we heard the popping noise when we just touched the light switch cover (didn't even flick the switch). The popping noise seems to be getting louder as well and more frequent in all of the switches. Periodically, we get a shock when we touch the switches as well.

What is causing this? Is it dangerous?
What should have an electrician look for or test for when they come?

Any suggestions that anyone has would be great.