Sudden playing of random sounds?

[Empress Misery]

I had Steam idling in the background and was talking to some people on TS when I heard a weird noise, like a tone from a game soundtrack. I though it was someone doing something on TS3 so checked the whisper list and nothing and the room was locked. I closed it and it continued, but a minute later I started hearing sound from a movie or something.

So I looked on the mixer to see where the sound was coming from and it was Steam. I checked for open voice chats on Steam (there were none), and closed anything else I had open (there were no browser windows). It was what sounded like the soundtrack from some early Jackie Chan film or something...

I checked the Resource Monitor for network activity related to Steam was stuff coming from and Stuff related to Steam.exe was:

cloud-2.steampowered.com @203kb/s
r1---sn-aigeznez.youtube.com @63kb/s
cdn.steamcommunity.com @46.5kb/s
rockpapershotgun.com @7b/s
cloud-3.steampowered.com @4.9
Media.pcgamer @4.3
Ihr14s2-in-f8.1e100.net twice at 342 and 25

There were no downloads started at the time, the Client was on the front store page (and minimized) and I had no community stuff open. I hadn't touched it for ages, and there was no open voice chats or anything similar. Changing pages around the store and changing tabs wouldn't stop the noise.

Exiting Steam made the sound stop, and when it restarted it was gone...

It was just weird. I'm not sure what steps cause it as it happened suddenly without any input from me, and as I did nothing obvious to make it start i'm not sure what would make it happen again. Maybe Steam is haunted! :D

On Win 7 64bit current Beta

[Bum ass fella]

Just had the "very nice" sound clip from csgo play suddenly. I saw the soundtrack player start up and it closed super quickly, then the sound played. very odd glitch