Clicking noise from my bettas?

I have two vailtail betta fish. One male one female. Both tanks are on opposite sides of my room. Now my female is new. I've had her for almost three weeks now. I noticed a week or so ago she will make strange clicking noises and first made sure she wasn't hitting something but it seems to be using her gills to make the noise. I can hear it accros the room at times. Today my male (about two years old) started doing the same thing. I've heard this can be related to eating food but they never do it when eating pellets. I'm wondering if it has something to do with mating. My male has always been one to make huge bubble nests and I suppose they could see each other from across the room if they wanted to. Howeve I don't think its anything health wise but I would like to know if anyone else has had the same issue.