Need help with mystery noise

[jorjef]

Do you have Bangii cardinals?. After I sold all the fish from my tank and got a little bored of looking at corals I bought two Bangii and ever since I have heard a similar sounds...Best I can describe is it like hearing from a distance a large marble banging around in a glass jar filled with water.. kind of a muffled sound. I think I have two males and the sound seems be around the time one fish is pestering the other.