my airtag made a odd sound

i just herd my airtag made a sound i never have herd that sound before and i looked in my find my app the battery is about to be dead and i just order some new batteres on Amazon and this is mine first time replaceing the battery in my airtag and i hope its easy to open the airtag and after i put new battrey in is my airtag still on my find my app let me know.