High-quality sound systems can be implemented over a virtually limitless, multi-zone area

Audio Combines Communication And Security

High-quality sound systems can be implemented over a virtually limitless, multi-zone area

Over the past two decades, many widely known incidents have occurred that have caused the loss of life. Emergency situations, ranging from the 9/11 attacks to fires to public stampedes at sports and religious gatherings, have caused various agencies to begin to analyze the weaknesses of all types of communications systems used in venues and transportation hubs worldwide.

Historically, such systems were focused primarily on fire alarm communications, but in relatively short order, the requirements have expanded into all areas of life safety and emergency communications.

Increasingly, these systems must comply with local, national or international codes and standards. In the United States, we typically see National Fire Alarm and Signaling code NFPA 72, and internationally we are beginning to see countryharmonized standards like EN54. Before the harmonized agreement, each European country had its own equipment standards. NFPA 72 has been revised many times, and in 2007 a definition for mass notification systems (MNS) was added. The Emergency Voice Alarm Communication System (EVACS) standard was written in 1985, but intelligible voice sound—not the old whistles, bells and tone signalling—was not included until 1999.

In regard to intelligibility, arguments have raged from all factions in the alarm and communications industry ever since NFPA mentioned the word. Intelligibility is not easy to quantify; it is a science requiring complex measurements.

However, if people in an emergency cannot accurately understand the messaging during a crisis, how are they, en masse, going to save themselves?

To improve public safety, NFPA is attempting to provide guidance through voice communication systems.

Achieving Intelligibility

It is the responsibility of the authority having jurisdiction (AHJ) to determine which spaces or areas require intelligible sound. Typically, AHJs don’t require intelligible voice communications in closets, mechanical rooms, kitchens and the like. However, it is unreasonable to expect the AHJ, typically a fire marshal, to understand the complexity of acoustical testing and interpretation of data required to determine if a system provides a good speech transmission index (STI) or a poor one. It requires an individual with the proper academic background and audio experience to measure and provide the STI data and the interpretation of the results.

If a region adopts NFPA codes, the AHJ is the person who determines if the installation, performance, reporting and supervision of the system meet all the required minimum performance specifications. The AHJ must certify the results in order for the building to receive a certificate of occupancy.

The EU standard EN54—which is not a law—is a product-standard requirement. EN54-16 permits the use of a voice alarm system for non-fire alarm purposes. This allows the system to provide messaging in a wide range of emergency events, such as a bomb threat.

EN54-24 details how a loudspeaker must be tested to verify the manufacturer’s specifications, including sensitivity, power handling, frequency response and environmental durability. EN54-24 also includes details regarding loudspeakers that must be operated with their dedicated or included active electronics.

Sound systems that are used to improve transportation security have the ability to improve the protection of people and property. These versatile and powerful systems can reduce the loss of life associated with risks such as natural, technological and man-made disasters. In addition, many of these systems can double their usefulness by providing recorded entertainment when they are not required to be a link in emergency communications.

Excellent sound reproduction is often distributed throughout sports venues, office buildings, theme parks, entertainment venues, shopping malls and waterfront gathering places. In the transportation sector, we see these specialized, high-intelligibility loudspeakers used in airports, train stations, rail hubs, highway inspection areas and marine applications such as ports, ferry terminals and aboard ships.

With the adoption of IP networks, typically via fiber-optical infrastructures, advanced, bidirectional audio/video communication systems can be implemented that are fully integrated with multiple points of control. No longer is it necessary to be stuck in a central equipment room to control vast systems.

High-quality audio and video can be implemented over a virtually limitless, multi-zone area. Networking allows the system to be linked over small or vast areas with high redundancy, high reliability and freedom from any interference.

Global Examples

Sound projection patterns from loudspeakers may be actively or passively controlled with a precision that would have been hard to imagine just a few years ago. Let us look at some of the ways that loudspeakers are used to protect passengers, workers and property against security threats, while providing communications for day-to-day use.

  • In Minneapolis, high-directivity, multiway horn loudspeakers are concealed within attractive decorative housings to provide clear announcements as well as emergency communications for a typically reverberant airport atrium.
  • At London Luton Airport in the United Kingdom, a complex multipoint control, multi-zone system delivers both paging and life safety. It ensures the smooth operation of the airport for approximately 10 million passengers annually while providing for their safety should the need arise. Loudspeakers are zoned and distributed throughout the facility, from its cathedralsized shopping malls to the long walkways to the gates. In each zone, the loudspeakers have been carefully selected for their power, coverage and ability to deliver high-intelligibility voice to every public area.
  • In Orlando, the Orange County Convention Center has installed both fire alarm and public address loudspeakers. In the event of an emergency, the fire alarm enunciators work first with automatic messaging. The message is then repeated on the public address system, which is far more intelligible.
  • In Venice, Italy, an audio solution has been devised to keep the whole city moving. Its tidal waterways on a daily basis re-map the routes accessible by waterborne taxis, buses and service vessels and, on what is usually dry land, by pedestrians. To provide advance information of water levels to the city, loudspeakers are located in 15 bell towers in central Venice and in 15 other locations on outlying islands. These loudspeakers play musical tones, which are now familiar to residents, and inform them of tidal levels so that they can plan to use routes that will be accessible. Venice was a custom project for the city planners, system designers, installers and the loudspeaker manufacturer, but it remains a great example of how well-implemented audio can solve a problem for an entire city.
  • In Seattle, train platforms use powerful weather-resistant fiberglass loudspeakers that have been coated to make them graffiti resistant. Although railway stations are wellknown as highly reverberant spaces, intelligibility can be maintained by using multiple close-proximity loudspeakers with well-controlled coverage, directing the sound to the people and avoiding highly reflective hard surfaces.
  • At Biga/Canakkale in the northeast coast of Turkey, IÇDAS port has two piers and a wharf with a total in-port berthing capacity of up to 20 vessels at the same time. Controlling ship movements is critical and complex, and the sea port is acoustically covered by a combined shore-to-ship control and safety warning system. Pole-mounted, high-directivity, weather-resistant loudspeakers provide the high sound levels needed with uncompromised intelligibility, enabling ship movements in the port to be controlled by verbal commands.
  • In Vancouver, British Columbia, an auto/truck ferry terminal loading area is acoustically covered with a very high-power voice loudspeaker system to provide instructions to vehicles—even if their engines are idling and their windows are closed.
  • At the Capitol in Washington, D.C., a roof-mounted public address perimeter system is installed that inherently has the control and power to be used for evacuation if required. The system provides intelligible voice well beyond a 1,000- foot perimeter.
  • Denmark, which has a relatively small population of 6 million, has installed a giant emergency management system. Nearly every person across the country is within earshot of the system’s acoustical coverage and messaging. The system was codeveloped by a partnership between American and Danish firms. Ten thousand sites throughout the populated areas of the country ensure even sound coverage.

It may be that the Danes are showing the direction for the future of large-area wide-acoustical security systems. These systems, in conjunction with digital signage, video surveillance, network control, cellphone messaging and intelligent analytics, can help in the battle to minimize security risks.

This article originally appeared in the Security Products Magazine - July 2012 issue of Security Today.


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