GL touts public-address system performance evaluation

GL field-worker-performing-speech-transmission-index-testing

Gaithersburg, MD. GL Communications Inc. has announced its capabilities in performance evaluation of public address (PA) systems. GL’s capabilities include test, design, and authoring specifications for transit agency PA systems. In addition, the company will evaluate the effectiveness of an existing system, identify deficiencies, and recommend improvements.

Gl Field Worker Performing Speech Transmission Index Testing 300x182
Field worker performing STI tests

Matthew Yost, a director of marketing at GL, said, “Over the past couple of decades, public address (PA) systems have added safety and security features in addition to displaying and broadcasting operational information. Some of these changes have been due to fire system evacuation requirements.”

He added, “Rail stations/platforms, large airports areas, and shopping malls are all examples where PA systems play an important role in alerting crowds during critical emergency situations. Many of these example locations have older PA systems that have fallen victim to time and environmental elements, dramatically degrading their effectiveness. It is also possible that the original design and installation did not provide adequate intelligibility and coverage. Even new installations may require field testing to verify the expected system results.”

Yost, further emphasizing the importance of the evaluation methods and services, said, “STI [speech transmission index] measurements, visual inspection and other operation checks, and transmission network evaluation should be strongly considered when the intelligibility and coverage of an existing PA system is in question or when new installations need to be verified for effectiveness.”

He further explained, “Speech transmission index…testing is a method of measuring speech intelligibility and is a widely-accepted algorithm in the PA system community. This testing is performed by transmitting a reference signal, known as the speech transmission index for public address systems (STIPA) signal, through the PA system and measuring the STI at every desired target location. These measurements are usually taken using a handheld device, and each measurement can usually be executed in 15 to 30 seconds. GL has provided STI testing services to multiple transit agencies, evaluating PA systems at rail stations and within rail vehicles. It is important to use the latest revision of STI standard (IEC 60268-16:2011 (edition 4), as improvements are actively being made.”

He continued, “Each speaker should be visually examined for obvious problems, sometimes due to environmental factors or age. Although a nonfunctioning speaker will be apparent while doing STI testing, GL performs individual speaker evaluations using sound pressure level meters. Other PA system components should be verified for operational effectiveness like amplifiers, DSP units, and fire alarm panels, which are commonly integrated with PA systems.”

He added, “PA Systems are often designed where a centralized control center is responsible for initiating announcements to remote locations. An example is a rail operator’s control center initiating live emergency announcements to remote stations on the rail line. The communications network between the two locations should be properly evaluated to ensure quality and integrity. This includes transmission study of end-to-end voice-quality measurements to evaluate the quality of live voice announcements and identify potential gaps or anomalies in the transmission network.”

He concluded, “Acoustic modeling methods within software can aid designers and evaluators of PA systems. Establishing the accuracy and reliability of the existing location’s acoustic model is critical before introducing any potential changes to the PA system.”

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