BY SCOTT BALTIC
Recent research and the experience of more and more fire departments indicate that mask amplifiers are the way to improve voice communication while wearing SCBA.
In the 31 years that Captain Mike Kreuger spent with the Pittsburgh (PA) Fire Department (25 as a captain), voice communication while wearing air masks was pretty dicey. “The louder you yell, the worse it gets,” he says.
Additionally, Kreuger says, the built-in speaking diaphragms on masks are too fragile. A little ice or a small crack—and forget about it.
Kreuger eventually developed and used a system of hand signals with his company. The setup worked for the most part, unless one of the regulars familiar with the system was off duty or out sick. Then somebody unfamiliar with the hand signals would fill in, which moved the company back to square one.
Effective, reliable fireground communication is essential for firefighter safety. The lack of it can kill firefighters and has done so at numerous incidents.
Poor communication is especially hard to explain or justify when firefighters are within earshot of each other or even in the same room. While wearing SCBA in such situations, they often can’t talk back and forth easily and reliably.
Mask amplifiers are gradually becoming more popular, but do they really work? Not only are more and more fire departments trying mask amplifiers and adopting them, but there now is laboratory evidence that mask amplifiers can indeed provide fireground voice communication that doesn’t resemble that of the drive-through lane at a fast-food restaurant.
AMPLIFIER TESTS
A recent study by two researchers proves that mask voice amplifiers make a significant difference, especially under the worst conditions. In a report released in September 2001, Marc Buchner, an associate professor of electrical engineering at Case Western Reserve University in Cleveland, Ohio, and Brian Buchner, of the University of Missouri–St. Louis, describe their research on speech intelligibility with National Fire Protection Association (NFPA)-compliant SCBA.
Their study examined the speech intelligibility performance of four manufacturers’ SCBA, with and without audio mask amplifiers, under two different background noise environments. Appropriately, the experiment was performed on the ground floor of a large warehouse, in a room with a tiled floor, concrete-block walls, and compressed-cardboard ceiling tiles.
Following the ANSI S3.2-1989 (R1999), Method for Measuring the Intelligibility of Speech over Communications System guidelines, the researchers used a Modified Rhyme Test. A speaker wearing SCBA read a series of 50 randomly generated sentences, each of which included a key word. For each sentence, five listeners seated five feet away then individually tried to pick the correct key word from a set of six sound-alikes (e.g., vest, test, rest, best, west, nest; save, same, sale, sane, sake, safe).
The five speakers for each mask were trained to speak at a relatively constant volume level (60 and 70 decibels for different trials); the background noise levels were also set at 60 and 70 decibels. With all four possible combinations of speaker volume and background noise, and experimental sets with and without mask amplifiers, there was a total of eight trials.
The researchers found that, regardless of the type of mask, mask amplifiers always increased comprehension scores for a given combination of speaking and background noise levels. Depending on the circumstances, the improvement ranged from seven to 33 percentage points in the average intelligibility score.
They also found that mask amplifiers consistently improved intelligibility when the background noise level was louder.
Buchner and Buchner concluded: “Significant speech intelligibility performance improvements are achieved for all four masks through the use of a mask amplifier and, furthermore … the most significant improvements occur under high-noise conditions.”
A TOUGHER NFPA STANDARD
Mike Kreuger is on the technical committee for NFPA 1981, Standard for Open-Circuit Self-Contained Breathing Apparatus for the Fire Service, the 2002 edition of which added some important changes. This version of 1981, he explains, toughens the current facepiece speech intelligibility requirement by increasing the background noise during the test and also by raising the minimum intelligibility percentage needed to pass. Of the six SCBA manufacturers tested according to these new requirements, one definitely passed, three narrowly passed, and two failed, Kreuger explains.
The object of the change isn’t to hurt the SCBA manufacturers, Kreuger says, but to challenge them to do a better job. “Verbal communication is rudimentary at best when you’re wearing SCBA,” he says.
GROWING ACCEPTANCE
Even before the NFPA moved to indirectly encourage the use of mask voice amplifiers, however, manufacturers that have introduced them have found their acceptance to be increasing.
Three to five years ago, fire departments simply weren’t interested in mask amplifiers, and the market for them was pretty limited, says Draeger’s Julie Malinowski. Since then, the systems have improved, and fire departments are more interested. Two years ago, only 10 percent of the Draeger SCBA sold were equipped with mask amplifiers, but now it’s 25 to 30 percent and growing.
The 9-11 attacks further increased fire department interest in radio interface systems, she says, because of the increased use of Level A protective clothing. The increase in the background noise in the revised NFPA 1981, Malinowski says, could also substantially boost the market for mask amplifiers.
In addition, representatives from MSA and Scott Health & Safety agreed that mask amplifiers are increasingly popular, especially because of how they improve firefighter safety at incident scenes.
Mask amplifiers appear to be best accepted when offered as an easily removable facepiece accessory. This enables departments to move amplifiers among users and preserves the mechanical speech diaphragm as a fail-safe communications backup.
Miami-Dade (FL) Fire and Rescue and the Houston (TX) Fire Department are just two departments that are very interested in mask amplifiers. In Houston, a pilot program with mask amps convinced the department of their worth, says District Chief Terry Stone, although budget reasons have been delaying acquisition.
Houston had some difficulties with feedback between the amplifiers and the lapel mikes for the department’s radios, Stone says, so the next test program will probably be with a new voice amp that’s shielded from radio-frequency interference. He advises departments that are considering mask amps to follow the same rule they would with any other new equipment: Test it thoroughly under local conditions.
That said, Houston is very happy with the results so far, Stone says. “I’ve never heard any negative words about the voice amplifiers.”
In Miami, following a couple of trial programs, the fire department is retrofitting integrated voice amplifiers to all of its almost 500 SCBA units, says Eric Hamilton, the department’s air truck coordinator.
“The communication is really, really enjoyed,” he says. “The guys seem to like it.”
SCOTT BALTIC is the editor of Homeland Protection Professional and the former editor of Fire Chief magazine.
