The Intelligibility Factor
A little over a year ago, the International Association of Fire Chiefs received several concerns regarding the operation of digital radios in high-noise environments common to the fireground. As a result, the IAFC formed a Digital Problem Working Group made up of fire service representatives, radio manufacturers, breathing apparatus manufacturers and members of the fire equipment industry to investigate these concerns.
The DPWG teamed up with the National Institute of Standards and Technology (NIST) and performed simulated environmental tests to establish a baseline comparison between analog radio communication and digital radio communication in high-noise environments. The DPWG’s work to date has produced a set of best practices and an interim report that summarizes its findings and outlines specific recommendations.
Until now, there has been an ongoing debate over the intelligibility of analog radios versus digital radios, but there has never been any testing as extensive or as scientific as that conducted at the NIST laboratories. While many have suggested that there should be “thumbs up or down” discussion on digital radios, that is not a realistic expectation. In fairness to the radio manufacturers, they all have met existing technical standards. There also is no other intelligibility performance standard by which to provide such a pass/fail measure.
It now has been proved that other firefighting equipment such as low-air alarms add challenges to fireground communications. Standards must be established that require new firefighting equipment to pass muster and not interfere with existing communications equipment. The firefighter’s personal gear (old and new) must be interoperable.
Now that digital radio performance challenges in high-noise environments have been validated, it is imperative to conduct additional testing with radios in other public-safety and public-service environments where high noise is likely. Testing is necessary to determine whether accessories such as remote or bone microphones exist that can immediately overcome noise and improve intelligibility.
Digital radio performance and intelligibility don’t stop with the fire service or public safety. The SAFECOM Executive Committee recommended to the Office of Emergency Communications and the Office of Interoperability and Compatibility that a national, multiple-discipline action team be formed to develop a digital radio audio intelligibility performance standard that considers the work environments of all public-safety agencies, including EMS, law enforcement and transportation. This intelligibility performance standard should drive the development of vocoder technology and associated communications software to achieve analog audio quality — or better — in digital radios. For public-safety responders, this audio quality standard will be necessary to transition successfully to 6.25 kHz.
Charles Werner is chief of the Charlottesville (Va.) Fire Department, chair of the IAFC’s Digital Problems Working Group and a member of the Urgent Communications editorial advisory council.
Intelligibility of Selected Radio Systems in the Presence of Fireground Noise www.its.bldrdoc.gov/pub/ntia-rpt/08-453
Portable Radio Best Practices www.iafc.org/associations/4685/files/digProb_PortableRadioBestPractices.pdf
DPWG Interim Report www.iafc.org/associations/4685/files/digProj_DPWGinterimReport.pdf