(1) Check the contacts on the charger and roomba (2) Remove battery and clean contacts there (3) There is a software issue (hold CLEAN to factory reset) (4) There is a hardware issue (get it repaired or replaced)
More reasons a Roomba can make these sounds are... (1) Voltage spikes are sent to the dustbin making it make a slight tick. (2) A software\hardware issue making the speaker make a tick sound (3) Faulty charger.
