I would be really surprised if its bats making the noise!! 13 years as a pest controller and I have had many such a call, every time it turned out to be Mice, Rats or Squirrels.
Hot to tell the difference between mice and bat droppings:
Pick up one single poo and rub it between finger and thumb, if it turns to powder it is bats, if it remains firm it is mice, if they are elongated about half an inch long and about 5mm thick they are probably rats, squirrel poo is similar to rats so you will need to look out for a large pile of insulation which will be the squirrel nest they will often have several nests made from rolled up balls of insulation.
If they are bats then look up a local bat group and they will advise you.
Good luck!!