WHAT DID YOU SAY?
VOLUNTEERS CORNER
Are any of your firefighters experiencing hearing problems? Do officers have difficulty hearing radio transmissions while responding? What are the cumulative effects of the noise that firefighters are subjected to each time they respond to an alarm?
If these questions are of concern to your department (and if they are not, they should be), the specifications for new apparatus should include some changes, and perhaps your current apparatus should be modified.
With the advent of “cab-over” and “cab-forward” apparatus, audible warning devices (airhorns, electronic and mechanical sirens) have been positioned on the cab roof. From a hearing standpoint, this is an extremely poor location-six inches from the ears of those riding in the cab.
Have you measured the decible rating in your present cabs? The new NFFA Standard 1500 Firefighter Occupational Safety and Health program recommends ratings of 85 or less for all new apparatus. If firefighters are currently subjected to a decibel rating average above 90, they must be issued and required to wear hearing protection in the form of ear plugs or muffs. Both Los Angeles City and Fairfax County, Virginia, have issued hearing protection.
Several apparatus specifications should be considered in an effort to help reduce hearing loss. First and foremost is the performance specification that recommends a maximum cab dba rating of 85 decibels at a speed of 55 miles per hour without warning devices in operation, or 90 decibels with audible warning devices operating.
Next, consider the location of audible warning devices on the apparatus. They should be mounted low, out front. They should not be mounted behind a decorative grillwork, or the sound will roll back into the cab. The sound must project beyond the sheet metal front of the apparatus. Hie entire horn portion of a mechanical siren that’s mounted through the cab’s frontal sheet metal must protrude from the cab and not come in contact with the sheet metal. If fastened directly, the sound will vibrate through the metal and into the cab. These installations require very good insulation around the siren motor to reduce cab noise. Electronic sirens should not be mounted to the cab sheet metal. If they are behind the bumper or above the gravel shield (the flat diamond plate between the bumper and the cab), the sound will be trapped and penetrate the cab.
The best locations for horns and sirens are the bumper or the gravel shield. For best results, insulate the horns and sirens mounted in the bumper. Although mounting these devices low on the vehicle does improve projection, there’s no proven advantage to angling them to the sides for crossstreet traffic. However, placing the de-⅝ vice at a downward angle, so the sound projects off the pavement, has proven^ detrimental: The sound bounces up jusU as the apparatus passes over it and resounds into the cab.
On conventional cab apparatus, si-i rens and horns can be mounted on the fenders, hoods, or bumpers and reduce the noise in the cab over the roof mountings. On “cab-forward” and “cabover” units with roof-mounted audible warning devices, some safety officers recommend rolling the windows up to reduce the noise; however, others feel that this reduces awareness.
Engine noise can also be reduced to lessen hearing damage. Several chassis manufacturers now make units with the motor mounted either at the rear or amidship, where the pump has usually been placed. This removes much of the noise from the cab. (This also removes | engine heat from the cab and provides! additional cab space.)
Existing units or new apparatus of! “cab-over” and “cab-forward” design canj reduce noise and engine heat by insulating the engine compartment. When de-1 veloping specifications for new’ appara-j tus, require that the cab be totally insulated-roof, walls, and floor. In the past, the floor has often been overlooked.
The NFPA 1901 Fire Department Equipment Committee and its Subcomj mittee on Safety continue to look for | ways to reduce noise, both in the riding compartments and at the pump panel. It is hoped that their efforts and the innovative attitude of the fire service will lead to better apparatus and reduce hearing loss. What’s that, you say?
