Zone planning in PA systems: examples for factories, hotels and malls

Why are zones needed?

In a single-zone PA system, every message is heard everywhere in the building. In a hotel, the front desk paging one guest disturbs people resting in their rooms. In a factory, an announcement meant for the loading area distracts everyone in a meeting in the office. Over time, people start ignoring announcements, and this habit carries over into emergencies.

Zones make sure a message reaches only the people it concerns. Each zone's volume and music source are set separately. While calm music plays in the restaurant, the lobby can have a livelier program. In a noisy production hall the volume is kept high, and in the office next door it is kept low.

In an emergency, zones become part of the evacuation scenario. The floor where the fire started and the floor above can get an immediate evacuation message, while the other floors get a stand-by message. This phased evacuation keeps the stairs from filling up and getting blocked all at once. How the scenario is set up is determined by the building's evacuation plan.

How are zones divided?

Zone boundaries are drawn on the floor plan and decided based on these questions:

• Is the area used for a different purpose? Office, production, storage, cafeteria
• Is the noise level different, and does it need a separate volume setting?
• Is different music or programming wanted?
• Is it a separate stage in the evacuation plan?
• Does it match the zoning of the fire alarm system?
• Is it an outdoor or an indoor area?

Expert note: Try to keep PA zones within the same boundaries as fire alarm zones. Whichever zone the signal from the fire panel points to, the PA system can send a message to the same zone; if the boundaries differ, the scenarios get complicated.

How is the priority order set up?

In a PA system, more than one source may want to play at the same time: background music, the microphone at the front desk, a scheduled bell or pre-recorded message, and an evacuation message from the fire alarm. The system must know which source takes precedence over which.

In a typical order, the emergency message comes before everything else. It is followed by the live announcement microphone, then scheduled messages, and music last. When an emergency message starts, the music stops and every area, including zones where the volume has been turned down, goes up to a preset level. A volume knob turned down in one zone must not cause the emergency message to go unheard.

Standards such as TS EN 54-16 for voice alarm and evacuation systems and TS EN 54-24 for loudspeakers define this behavior. Whether the system will have an emergency function should be decided before the zoning plan.

Factory example

In a factory, production halls, the warehouse, the loading area, administrative offices, the cafeteria and the outdoor yard are usually separate zones. Because machine noise is high in the production hall, more speakers are used in this zone and the volume is kept high. Narrow-angle, high-power horn speakers are preferred in noisy areas.

Scheduled bells for the start of a shift, breaks and the end of a shift can ring at different times in each zone. When vehicles are paged to the loading area, the offices do not hear it. In an emergency, however, an evacuation message is played in all zones at once and the assembly point is announced.

In the outdoor yard, wind and vehicle noise scatter the sound. Outdoor speakers should be resistant to rain and dust, and their direction and angles should be set to keep sound from spilling over into neighboring plots.

Hotel example

In a hotel, the lobby, restaurant, pool, spa, meeting rooms, corridors, staff areas and parking are planned as separate zones. Guest rooms are kept out of everyday announcements and music, but the emergency message must be heard in the rooms too. That is why speaker placement in the corridor zones is designed so the message can be understood from behind the room door.

If the meeting rooms have their own sound system, a link is set up so that in an emergency this system is muted and the emergency message is played in the room. Otherwise, a loud presentation in the room could drown out the evacuation announcement in the corridor.

Staff areas should be treated as a separate zone. Internal announcements for the kitchen, laundry and technical service should not be heard by guests, but in an emergency the staff in these areas may be the first group alerted. In a plan where staff help guests during evacuation, the content of the message sent to staff zones is also prepared separately.

Shopping mall and large store example

In shopping malls, common areas, floors, parking, the food court and staff corridors are divided into zones. Stores may have their own music systems. It should be planned that in an emergency these systems are cut off and the central PA system can also be heard inside the stores.

In high-ceilinged atriums, echo is strong and speech intelligibility drops. Here, using more speakers running at a lower level gives a clearer result than a few loud speakers. Parking levels need separate settings for vehicle noise and concrete surfaces.

Cabling and expansion

Each zone's speakers are connected to the central unit by a separate line. In systems with an emergency function, zone lines can be run as two separate lines, A and B, so that a fault on one line does not silence the whole zone. The lines are installed so that they can be monitored for faults.

The number of zones determines the capacity of the central unit. If a new building, a new floor or an area to be divided is planned for the future, the central unit is chosen with spare zone capacity. Splitting a zone in two later means running a separate line; if this possibility is considered from the start, there is no need to open up the ceiling again.

Next to the central unit, there should be a diagram and labeling showing which line goes to which area for each zone. When a speaker in a corridor goes silent, finding the fault takes minutes if this document exists. Without it, the technician has to trace the line ceiling by ceiling.

Frequently asked