Bats emit a chattering sound when flying that is similar to a cricket's chirp. Bats also emit high pitched squeaking sounds when in distress. Bats can also be detected by the flapping sounds their wings make when in flight.
When bats make their way into homes and become trapped in attics or crawlspaces, it is common for bats to scratch and thump on the internal walls, according to Allstate Animal Control. Bats scratch on the walls when they are disoriented or in search of an escape route.
While bats do not attack people instinctively, they do bite when in distress. Bats are known to carry rabies, so it is a good idea for homeowners to contact a professional exterminator in the event of a bat infestation.