Laptop battery makes high pitched noise when installed - no cable plugged in, and not turned on

Hi all, I took my laptop battery out like I normally do to check for dust in my HP Elitebook earlier, and noticed that when I put it back in it makes a quiet high-pitched squealing whine. The laptop is powered off, it's not plugged in, and the noise only happens when the battery is inside - I think the noise changes slightly when I lock it in place. Does anyone have any idea what this might be? Is it okay to use?