I don't think that the bladder is leaking, or things wouldn't be functioning properly. What you hear may just be the normal operation of the pressure tank. Water goes in and out of it all of the time against the air-filled bladder.
To check the bladder, turn off the pump, drain the water pressure off, and check the air pressure of the tank with a tire gauge. (If the bladder is leaking, water will probably come out of the air valve of the tank.) If no water comes from the tank air valve, it should read two psi below your pump cut-on pressure (i.e. if your pump is set at 30/50 cut-on/cut-off, the pressure tank should be at 28 psi).
If it is low, air it back up with a bicycle pump or portable air tank or compressor. If it doesn't hold that pressure, then the bladder is probably shot, and you need a new pressure tank. You can usually replace a bladder, but replace the entire tank instead.