@BagelFPV discharge it as far down as you feel safe. Then bring it to a place where you can dispose it. In Australia it seems that you got multiple ways.. even ALDI will take it (from a Google search). Do not dispose it through your household trash..
@M4R5_FPV ok, will do, didn't know whether lipos could be disposed of like normal batteries, thought you needed to go to an e waste facility or something
as for the sound i would check if the frame is cracked or if a prop is bent,... another issue could be a bent motor. to test it: props off!! - connect to betaflight - connect a lipo - go to the motors tab in BF - spin up one motor at a time... if one sounds different you found the cause...