Beeping sound saying "low battery" what is this?

i am doing school so this is very annoying. my mom said that it is probably ether the thermostat or the smoke detector and it sounds like it is coming from the stairs so it is not the smoke detector and it sounds like the thermostat cuz it will beep and something else will say low battery it is crazy loud what can I do to stop this it is too loud to change the battery and I don't know what battery it takes pl help! I am going insane!
i know that its under the wrong category but I don't know where to put it.