Is it normal my bf makes this weird sound before he 'orgasms'?

Basically..or usually every time we have sex, and my boyfriend is about to cum, he makes this interesting sound that let's me know he's seconds from finishing. I'm not really sure how he does it because I'm usually going down on him as he's doing it..
It sounds like he has his tongue in his cheek, and moving it around a lot seems to make that sound haha like a ..wet, not really "slurpy" ..idk I'm not sure how to explain it lol

But I was just wondering if any other of you guys make sounds similar to that, or if its even a common thing?
I'm just curious :D