Is there voice chat? (I'm hearing voices...)

So basically, the other night I was up pretty late playing a match of League trying to get some IP. I was on Summoner's Rift, Intermediate bots. While I'm jungling with Master Yi out of nowhere I hear a very faint voice go "Oh come dude, this is horseshit". I don't know what it was, but I know it wasn't any other programs on my computer and it wasn't IRL. I heard it through my headphones and it sounded like an actual person. I know this seems like bullshit, but it isn't. It's happened to me twice, the first time was when I first started playing. I thought it was just some random noises but now that I think about it I don't think any noises in League sound like a kid yelling "fuck".

[slayer-jinx-unamused]

Anyways, I decided since I couldn't find anything about this by looking it up I would make a discussion about it. I have no idea what category this would be under, and I'm pretty new when it comes to the League community. If anyone knows what the actual fuck is going on please tell me, or else I'm admitting myself to a mental institution.