device plugged-in / unplugged when turning on TV monitor

I have an eGlobal Mini-PC which includes an Intel HD5500 grahpics, coected via HDMI to a LG 42LD460 TV. It generally works well, but:

• When I tu the TV on, the PC make a "device coected" and then a "device discoected" sound.
• When I switch the TV to another HDMI input, the PC continously makes "device coected" / "device discoected" sounds through its speaker - I have to mute those to avoid it.

This TV didn't have this issue with my previous PC, which had an AMD Radeon HD4650, also coected via HDMI.

Questions:

1. How can I determine what device is being coected/discoected? I looked around in event viewer, but didn't find anything.
2. How can I avoid these sounds?