Evaluation and Testing of Public Address Systems at Metro Stations

Welcome to an April 2009 issue of GL's consulting newsletter. In this issue, we focus on evaluation and testing of public address (PA) systems at metro stations.

Speech intelligibility is an important characteristic to be considered in the design of Public Address (PA) system. A PA system in a metro station or a public transit center is used to announce train or bus arrival/ departure, general information, and emergency information and instructions to passengers. Poor speaker characteristics, inadequate sound levels, reverberations, and delays can degrade sound quality and make even an expensive sound system perform at a subpar level. Addressing these issues at the design stage through proper planning and acoustic simulation studies would improve a PA system's overall performance and customer satisfaction, and minimize the need for expensive post-installation modifications. Evaluating an audio system and coming up with a design to improve its intelligibility are specialties that are best handled by acoustic experts.

A Case Study

Recently, a public transit operator of a large metro train system utilized GL's expertise in evaluating their PA system at select above-ground metro stations. The PA system required improved intelligibility and additional coverage in order to address adverse customer feedback. GL conducted a comprehensive study to (i) assess the existing system and (ii) recommend steps to improve speech intelligibility and coverage at the metro stations. We made our recommendations based on the need to meet or exceed NFPA 72/2006 requirements for an industry standard Common Intelligibility Score of 0.7.

GL's engineers used Speech Transmission Index for Public Address (STI-PA) standard to assess speech intelligibility objectively. Enhanced Acoustic Simulator for Engineers (EASE) software was used to conduct simulation studies and recommend steps to improve intelligibility and increase coverage area. Our engineers created 3-D computer models using as-built drawings and detailed site measurements. With the use of 3-D models and ambient noise measurements, acoustic environment of the areas requiring PA coverage was simulated. We analyzed the results of simulations studies and recommended optimal speaker type, locations, and power levels.

Please click here to obtain more information about GL's study.

Customer Benefits

GL's recommendations would greatly improve the speech intelligibility of the existing PA system and increase its coverage area at the metro stations. The quality improvement would benefit the patrons leading to increased satisfaction.

Telecom Testing Solutions by GL

GL offers a comprehensive suite of testing services to evaluate complex networks. Our engineers have extensive experience to perform the entire gamut of testing that includes designing test plans, developing test procedures, conducting tests, and documenting test results. Our services are very cost efficient and include:

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