Background noise levels on the fireground

An important part of signal detection and distinction is the strength of the signal compared to the levels of the background noise. On a fire scene, firefighters use a Personal Alert Safety System (PASS) device to locate trapped or injured personnel. When a firefighter becomes incapacitated, the device emits an audible alarm to help rescue teams locate the downed firefighter. This device has proven to be an invaluable part of a firefighter’s equipment. However, there are cases in which the signal was not heard or localizable. It has become apparent that scientific research is necessary to improve this signal. The approach taken to investigating this environment is to use the passive sonar equation as a template. An important piece of this research is the background noise levels that are routinely found on an active fire scene. Much of the equipment used by firefighters acts as high intensity broadband noise sources. Measurements were taken to investigate the frequency, level content, and directionality of the equipment used on the fireground. The A-weighted spectrum of the equipment has then been compared to the signal emitted by a PASS device. [Work supported by U.S. Department of Homeland Security Assistance to Firefighters Grants Program.]