The CT-ANS background noise sensor is designed to measure ambient noise to help adjust the volume level of the voice announcements to the measured noise level in the zone of operation of the public address system in a given zone. Based on the CT-ANS sensor measurements, the public address system maintains the volume of the emitted sound (announcement, information) in the zone for a specific setting. This allows intelligible announcements to be made at an appropriately adjusted volume level. The sensor measures ambient noise using a built-in professional microphone.