Found everywhere from warehouses to schools to grocery stores. Comprising of speakers on poles or hanging from the ceiling joist or flush with the ceiling tile. You also need an amplifier and a microphone. If you wish to have a good sounding PA system you may want to get a basic equalizer.
Similar as to what a PA system can do, but for more refined. Here music serves many marketing purposes. Every brand of store has its own vision as to what that is. Thus the technology behind this is more sophesticated. Head office wants to control all sources of media that is presented to the their customer base. So our simple PA system has become better sounding and offering alot more.
Their are many applications where we can use this technology. Lets look at commercial application with back ground music. This allows you to keep your customers shopping longer. They are quitely listing to Chopin and they can barely hear the sounds of the mall.
Other uses include privacy for such areas as open space office, government facilities, financial institutions, hospitals,etc where conversations are wanted to be kept private and not heard on the otherside of the room.