The acoustic properties of SCBA equipment and its effects on speech communication

In assessing system requirements for effective communication in public safety applications, a number of challenges exist. The Self-Contained Breathing Apparatus (SCBA) mask air-delivery system is essential equipment in certain public service activities, mainly firefighting and HAZ-MAT (hazardous materials) operations. It is important that high-quality and reliable communications are maintained when SCBA equipment is employed. An SCBA mask encloses the face and mouth, which alters articulation and distorts the speech spectrum. SCBA system noises such as alarms and air-regulator noise, in addition to environmental noises, add to the deterioration of speech quality in an SCBA-fronted communication system. A digital speech codec adds another potential source of speech distortion and diminished intelligibility when noise-corrupted speech is processed. This article characterizes some of the effects of SCBA equipment on speech quality and intelligibility in the context of a radio communications system and outlines parameters that should be considered in communications system design and interfacing.