Columbian shark making weird noise Question

Well I went to check on my columbian sharks in there indoor pond, and heard this weird clicking/burping noise it kinda sounded like they were bouncing off the walls of the tank, but when I looked they were just swimming nice and calm and I could still hear this noise, is this the noise they make, because I don't think iv ever heard it until maybe now,

 

It could be totally normal for the fish to make those noises. My loaches all click when I feed them, sounds like nails tapping on the glass, and my raphael catfish makes grunting noises. Its kinda fun to listen too.