Wolf pup 16 ft 2022 outdoor speakers humming

So I have a weird one, camper dose not have batteries in it. But outdoor speakers are making weird humming noises when it's cold out like 0 and below. And sometimes when it's like 32 out. Not sure why but it is. There is no power source the solar is not hooked up either. Any ideas??

Will we need new speakers in the spring time??