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NIJ (National Institute of Justice) Standard for Emergency Vehicle Sirens

NCJ Number
Date Published
This standard establishes performance requirements and test methods for electronic and electromechanical sirens used on law enforcement vehicles to warn pedestrians and motorists of the passage of an emergency vehicle.
The standard establishes two classes of sirens, based upon acoustical output. Class A sirens provide as a minimum an A-weighted on-axis sound level of 120 decibels (dB), and class B sirens provide as a minimum an A-weighted on-axis sound level of 115 dB. Definitions are given for terms used in the standard, including anechoic room, automatic operation, A-weighted sound level, wail, and yelp. Equipment requirements are listed, including general requirements, operating life, acoustical performance, and environmental performance. In addition, test requirements are delineated for such important elements as testing procedures, inspection, wattage test, environmental tests, and postenvironmental tests. The environmental tests encompass those for high and low temperature, dust, moisture, corrosion resistance, and vibration. Tables are provided. Six references and information and diagrams on measurements of the acoustical output of emergency vehicle sirens are appended.