The PRO 31 is suitable for heavy industries such as metal forging, stamping, cutting, shipbuilding; semi-conductor industries such as diesel uninterruptible power systems, compressors, compressed gas production. Transportation industry such as ship turbines, diesel engine rooms, airport ground crew, aircraft maintenance personnel. Construction sites such as excavators, pile drivers, large screw factories, metalworking factories, etc. The PRO 31 is also suitable for heavy industries such as forging, stamping, cutting, shipbuilding, etc.
The PRO filter has a unique two-way conduction feature that dramatically reduces the "blocking effect" of wearing earplugs, allowing you to hear your own natural voice when you speak. The two-way conduction also keeps the ear canal well ventilated and comfortable.
(The blocking effect is the feeling that the sound of your own voice echoes inside your head when you plug your ear canals).
The chart below shows PRO 31's attenuation curve. As you can see, at 115 decibels of ambient noise, the PRO 31 filter can provide up to eight hours of safe listening time. The next chart shows the safe-listening-time of different PRO model filters under different ambient sound pressures. If the PRO 31 doesn't give you enough safe listening time at your ambient sound pressure, you should add a pair of overhead-earmuffs to provide a higher noise reduction factor.