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Effective Notification with Public Address Systems
The Editorial Team2010/3/23

Communication plays a crucial role in ensuring safety. A clear and direct command during emergency prevents chaos and minimizes possible casualties. A&S takes a look at the latest technologies, trends and challenges of the current public address market.

Communication plays a crucial role in ensuring safety. A clear and direct command during emergency prevents chaos and minimizes possible casualties. A&S takes a look at the latest technologies, trends and challenges of the current public address market.

The market for public address (PA) and voice evacuation (EVAC) systems is growing steadily. "The worldwide EVAC systems market is estimated to be worth US$37.5 million in 2009," said Alastair Hayfield, Research Manager, Video Surveillance and VCA Group, IMS Research. "More than half of the sales for these alarms are believed to come from the Americas market."

The market size increases for all types of PA systems. "We estimate the worldwide market for PA systems to be worth more than $10 billion," said Kaz Shimizu, Product Marketing Manager, TOA. "Since all new buildings require such systems, developing countries such as China, India and Brazil are seeing the strongest growth."

The economic downturn has had little effect on the market. "The slowdown in new construction might have a minimal effect on the EVAC systems market; however, the main vertical markets that tend to use these systems are schools and governmental buildings. Many of these buildings will present retrofit opportunities," Hayfield said. "In the U.S., one of the EVAC drivers will be the new NFPA 72 code for mass notification."

Applications for PA and EVAC systems range widely, with unique requirements for each market. "It is hard to describe a standard set of systems because installations for PA systems are of ten highly customized," said Penny Wu, Marketing Manager, BXB Electronics.

PA systems are divided into two categories — commercial and emergency. Providers of notification systems usually have the R&D know-how and industry experience to offer solutions for both categories.

Commercial Systems
Commercial PA systems must be flexible for varied usage. Functions such as background music at shopping malls and theme parks, discount notifications at supermarkets, broadcasts of church services and announcements at schools all require tailor-made systems.

In both digital and analog systems, amplifiers play an important role. Configuration can be done by zones and users can choose between prerecorded messages, live-announcements and message recording.

A network control unit is the heart of a digital PA system. "Our network controller monitors the status of all the equipment in the system, reports status changes and stores fault messages in the system," said Terence Ng, Senior Product Marketing Manager, Public Address and Conference Systems, Robert Bosch (SEA), Bosch Security Systems. "This monitoring extends from the capsule of a call station microphone to the end of a loudspeaker line. The external cables connected to the control inputs are monitored for short and open circuits with an internally generated pilot tone for audio outputs monitoring."

Emergency Notification
Emergency notification is the highest priority. Traditional systems only sounded a siren throughout the whole building, regardless of location. Panic can cause injury, and reducing survival rates.

"In overcrowded environments, an adequate sound broadcast system is paramount," said Marco Morimanda, Product Manager, Paso. "When activated from the fire-detection system, it should be able to manage any emergency situations, allowing a guided and controlled evacuation of the premises."

Integration enables alarm notifications to be more precise, indicating location, type of danger and evacuation directions in calmly spoken live or recorded messages. "Implementing when-and-where automatic gain controls on paging microphones and system inputs improves user comfort," said Antonio Ferrari, Audio Contractor Market Manager, RCF.

System design must consider hierarchy. "Our amplifiers that run at 4 ohms or at 75/100V are ideal," said Grant Murray, Product Marketing Specialist,  Phonic. "The 100V high-output ceiling speakers and zone mixer allow emergency interruption functions, so emergency announcements are made efficient."

Integration makes evacuation easier. "For hotels, integrating video surveillance with PA systems allows security personnel to check the fire location and only evacuate tenants in specific areas," Shimizu said. "Managing a building by sections makes evacuation more efficient by not disrupting business flow at other locations."

Sound Clarity
A clear message enables effective information sharing. "To ensure sound clarity, a clear source of the message, good amplifiers, easy routing of audio signals, proper speaker types and positioning of the speakers are important," Morimanda said.

Microphones and speakers directly affect sound indelibility, acoustic feedback and echo. "Live announcements should use a good microphone with a smooth frequency response, such as electret condenser microphones," Ng said.
"A low-cut filter is often required to remove the bass boost that occurs when speaking very close into a cardioid microphone. This bass boost is called the proximity effect and would decrease the intelligibility of the announcement."

The sensitivity and input power of speakers vary the sound pressure level (SPL). "Enough sound volume — not excessive — is an indispensable factor to catch speech clearly," Shimizu said. "Therefore, the speaker's direction, angles, positions and input-power should be carefully considered."

To prevent extreme volume differences due to speaker placement, sound quality is maintained with appropriate product selection and acoustic design. "Our DSP keeps the setting parameters in memory, and the suitable adjustment pattern can be instantly recalled with a preset button," Shimizu said. "This feature ensures constant sound quality and prevents the destruction of equipment by operation errors. SPV simulation software further assists to calculate the estimated SPL at listening points and helps to decide the types of speakers used and system layout."

Speaker type and positioning is linked to sound clarity, especially for large spaces. "In smaller rooms and corridors, ceiling loudspeakers work well and are an economical solution," Ng said. "For larger spaces, the loudspeakers should be more directional to address the public without too many reflections from walls and ceiling, as this would cause echoes and reverberation."

Column loudspeakers are designed for this purpose. "In very large reverberant spaces, such as airport terminals, active column (array) loudspeakers with electronic beam steering are often the only practical solution to address people with clear intelligible messages," Ng said. "These array loudspeakers are capable of creating a very flat direct sound field precisely at ear level of the audience."

Large spaces require customized solutions. "For large exhibition halls, high-ceiling warehouses and other similar spaces, a hemispherical loud speaker is a good and economical solution. As the name implies, a hemispherical loudspeaker radiates 180 degrees wide into one direction, normally downwards, with an almost flat frequency response," said Ng. "For a clear sound it is important that the frequency response is not only reasonably flat on-axis, but also off-axis. The off-axis response is the area where the good loudspeakers distinguish themselves from the lesser ones."

Reliable power affects sound quality. "Amplifiers are designed to amplify small voltage input signals into much larger output signals," Murray said. "The audio circuitry must be capable of amplifying the input signal without alteration.
Since the power that drives the loudspeakers comes from the amplifier's power supply, a clean source of power is required to deliver a clean music signal."

Cabling also impacts sound clarity for all PA systems. "The width and material of cables must consider the distance for signal transmission," Wu said. "Cables must be tested to ensure its quality and color can be used for easy management."

Compatibility is a determining factor for sound clarity and smooth system operation. "According to different projects, installers need to consider how to select individual products at the design stage and test for compatibility," Shimizu said.

Rules and Regulations
Sales of notification systems are directly affected by rules and regulations. Providers must have sufficient knowledge of each country's requirements before manufacturing or releasing a product.

Requirements also change with time. "For example, we previously offered wireless systems that used the 700-800 MHz frequency range in the U.S., but due to change of regulations it's no longer available to manufacturers of wireless gear. We're now shipping units with frequencies above 833 MHz to the U.S.," said Murray.

Regulations affect system design. "In Europe, the EN 60849 and EN 54-16 and EN54-24 are common standards for voice alarm systems," Morimanda said. "The EN 60849 standard defines design and installation terms for the system to meet safety and reliability requirements."

Other standards for notification include Australian Standards 60849,
Singapore CP25, China Compulsory Certification Mark and Korea Certification Mark. Global standards may also apply, such as ISO, BS, UL, CSA or CE.

Japan has specific regulations. "There are three types of Japanese standards or regulations for PA systems," Shimizu said. "The safety standard compliance is mandatory for almost all electrical equipment. The emergency evacuation law decides the system features and acoustic conditions for emergency announcements. The construction rules control the architectural strength of installation, such as mounting brackets for speakers in the event of an earthquake."

Growth for PA systems is closely tied to standards and regulations. "PA systems for emergency sound systems need to comply with various international and national standards, with respect to functions, indicators and supervision," Ng said. "This is a continuous process, as standards are being revised and replaced regularly."

However, there is no single certification body for worldwide voice alarm standards. A global provider has to be certified multiple times with different bodies, slowing down the time to market, Ng said.

Changes in user preferences and market demand are other challenges for manufacturers. "The market is extremely broad, yet everybody has a different and specific idea of what they want and what they need their equipment to do," Murray said. "Trends and government regulations in different countries are constantly changing. Coming up with something new and innovative is always a challenge."

Easy user interface with more functions means a complex system backed up by solid R&D know-how. "The use of a single PA system for various functions, like background music, business announcements and voice alarm can be a challenge," Ng said. "Issues might be that clear voice announcements require a different tonal balance than background music. To resolve this, multiple parametric equalizers would be needed."

Future Outlook
In the future, standards and regulations will continue to play an important role in the PA market. Several manufacturers are waiting for the release of EN 54-19.

Device technology will continue to progress. The radiant degree of digital speakers will improve to 360 degrees with stronger audio processing, controlling, managing and powering, said Ferrari.

Market demands change with user expectations. "PA systems for emergency sound systems and sound reinforcement systems are moving into each others territory, as customers want a single system for both functions, such as sports stadiums," Ng said. "This means that PA systems may incorporate low-impedance amplifiers next to the traditional constant voltage amplifiers, but still with all supervision functions, including fault logging, amplifier redundancy and the ability to operate on backup power supplies."

Networking for digital PA systems will be more flexible, moving from proprietary network to standard Ethernet-based networks. This would not guarantee interoperability between different brands, but traditionally separated systems will be integrated to a certain extent, such as audio systems, video surveillance, access control, building management, Ng said.

Apart from that, telephone broadcast, intercommunication and security will also be more closely integrated. Systems will become more flexible with modular designs for easier maintenance and system upgrade, Wu said.

Data security grows in importance with the introduction of open network. "Future systems will need to be more secure, partly because nonproprietary easily accessible networks will be used, and also because of an increased risk of attacks by hackers or terrorists," Ng said. "This means additional functions are required for authentication and encryption."

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