The purpose of the hearing screening is to quickly test one part of the hearing system to find out whether it is working properly. Diagnostic hearing testing uses the same methods of testing but checks more frequencies and levels. Screening take less than 10 minutes, while diagnostic testing is more detailed and takes two to three hours because all parts of the hearing system are checked. Testing is done while the baby is asleep. It may take more than one appointment to get all the testing done. Your audiologist,- a person trained to check hearing, can explain all the tests, why they are being done, and what was found.