Tech Talk: The Quest for Intelligent Speech

How many times have you been in a public place and heard an announcement that was impossible to recognize? What if the message was an evacuation order for assistance in exiting a burning building? Learn the critical facets of speech intelligibility and how to test for it.

A reminder when selecting test equipment: components have various levels of calibrated tested precision. There is often a good reason why some devices cost more than others. You should carefully check the equipment specifications as to what is required by your AHJ, and make sure the equipment you select meets those testing performance criteria. 

While we have mainly emphasized testing guidelines, I would like to offer a few speech intelligibility performance suggestions. How can you improve speech intelligibility if you have poor test readings? Some ideas: use more speakers at lower wattage taps; calibrated amplifiers; speakers 20 feet or less from listeners; have all speakers in phase; audio wiring with an audio twist; correct speaker spacing to ceiling height; and checking reference standards such as NFPA.

A special thanks Gold Line’s Mathew Miller for contributing a variety of valuable training and technical resources for this article. He also mentioned the company will have a new and updated set of online training videos to look forward to this fall. Keep an eye out for that and learn more about opportunities in MNS speech intelligibility.

Bob Dolph has served in various technical management and advisory positions in the security industry for 30+ years. To share tips and installation questions, E-mail Bob at [email protected] Check out his Tech Shack blog at www.securitysales.com/blog.

 Tech Talk Tool Tip

Remember, speech intelligibility is not a physical quantity like amperes, volts or BTUs. It is the degree to which we understand spoken language. This month I have selected the Gold Line DSP2B system for speech intelligibility testing and recording. The kit comes with the company’s Platinum software shown here.

STI measurements can be made without significant training. Once the STIPA signal has been inputted to the system under test, a single button push on the DSP2B/BP will produce the STI, which can be converted to CIS as specified in IEC standard 60849. The test only requires about 15 seconds.

About the Author


Bob is currently a Security Sales & Integration "Tech Talk" columnist and a contributing technical writer. Bob installed his first DIY home intercom system at the age of 13, and formally started his technology career as a Navy communication electronics technician during the Vietnam War. He then attended the Milwaukee School of Engineering and went on to complete a Security Management program at Milwaukee Area Technical College. Since 1976, Bob has served in a variety of technical, training and project management positions with organizations such ADT, Rollins, National Guardian, Lockheed Martin, American Alarm Supply, Sonitrol and Ingersoll Rand. Early in his career, Bob started and operated his own alarm dealership. He has also served as treasurer of the Wisconsin Burglar and Fire Alarm Association and on Security Industry Association (SIA) standards committees. Bob also provides media and training consulting to the security industry.

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