Rubbers with harder topsheets and sponges often produce that sound. It may not be a bat problem but a stroke problem, if your contact is more direct and you are hitting more horizontally and flat then the sound will be quite sharp. If you are brushing the ball more and producing more contact then the sound will be softer, Hexer is quite a good rubber for offense and speed from the sponge and spin so it's possible that the change in rubber is causing the different sound. Try borrowing someone else's bat to play with and see if it still happens, in which case it would be a stroke problem not a problem with the bat.
If it's a carbon blade you can tell if it is broken by holding the blade on the sides loosely with the handle pointing upwards, slowly rock the bat so the handle swings forward and backward and then gently hit the handle against your forehead (sounds silly but it works). If the bat makes a crunchy vibration sound then the carbon sheet is broken and your blade is useless. If the sound is a softer vibration then it is ok!
Hope these ideas help.