Public address systems or PA systems are specially designed mixer, amplifier, and speaker combinations used to communicate with an audience. Typical speakers like portable Bluetooth speakers are used to simply play back prerecorded audio, like streaming music. So, what is a PA system, exactly, and how is it different? PA systems are more advanced than regular speakers, as they can enable live sound for multiple audio sources and can blend and amplify these sources to achieve a unified mix. It is also use as fire alarm hooter