A sound detector is designed to detect noise levels exceeding a certain decibel.

Many security incidents are initiated by some form of noise including gunshots, aggressive behavior, or breaking glass. Sound detectors must comply with applicable standards, such as ANSI/UL 639, Standard for Safety for Intrusion-Detection Units.

According to UL 639, Section 67.1.1, a sound detector system for a premises “may be used for use in buildings of substantial masonry construction.

67.1.2 A sound detector system for vaults may be used for nonreverberant application, reverberant application, or both.

67.2.4 A sound detector system intended for use in premises shall respond to impact noises 30 decibels above ambient, to any total noise level exceeding 70 decibels, or to both, as measured at the sound detector.”

Below is a sample of NFPA 731. For the complete section, see the actual NFPA 731 text at NFPA.ORG. Once there, click on the free access link to the latest edition of NFPA 731.

5.3.3.1.7 Sound Detectors. Sound detectors shall be in compliance with applicable standards, such as ANSI/UL 639, Standard for Safety for Intrusion-Detection Units.