Transportation hubs, such as airports, train stations and bus terminals, require intelligible announcements and provide an indispensable service to help passengers and anyone who meets or sees off passengers to accomplish their objectives. Airports are divided into areas for each process in the flow of arriving and departing passengers, and announcements should be distributed to the appropriate areas according to each purpose. In a well-designed system, paging zones are set up for each area. Microphones with zone selection are properly placed and programmed as a priority function to precede others in case of emergency or superiority. Backup power sources, drives emergency announcements during power failures, and pre-recorded evacuation instructions can be automatically broadcast in coordination with fire alarm systems.

The main purpose of an audio system at in these busy hubs is to broadcast proper messages clearly to the people who need information. The sound system design needs acoustical approach as well as functional configuration. For the optimum intelligibility of announcement, the sound level of broadcasting needs to be 6 to 10 dB higher than ambient noise and the direct sound should be much louder than the reflection. However, many facilities are filled with ambient noise, echo and long reverberation, consequently announcements are prone to be unclear. In those areas the speakers must be appropriately selected and located according to the architecture and ambient noise. Line array speaker helps reduce echo and reverberation. Ambient noise controller is a convenient tool to automatically adjust the suitable announce level according to fluctuating ambient noise.