Frag Out! Magazine
Issue link: https://fragout.uberflip.com/i/693549
Semi-active earplugs The in-ear earplugs which are a development version of the simple silicone earplugs. A step towards the ac- tive hearing protectors, equipped with the electronic filters. There is no electronic used in the design of the semi-active earplugs, and the selected sound frequen- cies are damped due to an application of the laws of physics. A hart of the semi-active earplugs is a filter in the form of the channel situated inside the earplug. A suitably selected diameter of a hole causes that sounds with an intensity level which may be a potential thread for hearing are cut off, and there are transmitted only harmless sounds, for instance speech environmental sounds (up to a certain level of intensification). The earplugs offer a possibility to be turned off the filter and then you can use them as the ordinary silicone inserts described above. The semi-active earplugs are most often made of sili- cone what greatly facilitates their maintenance – they are reusable and they do not belong to the cheapest ones. They are also not the exaggeratedly expensive, their price fluctuates within the following limits: $10- 20. An average attenuation level of the semi-active earplugs is equal to the NRR of 23–25 dB with the closed filter (with the opened filter a level of the NRR is approximately 7–8 dB). The manufacturers usually recommend opening their channel during shooting, and closing it in the places where there is continuous, burdensome sound (for example, loading a transport aircraft). The filter is turned off in the different manner, depending on the design of the earplugs. The oldest version of the hearing protectors of these type – the first model Peltor Combat Arms Earplugs (CAE) consists of the two fir trees connected with their bases – yellow and green one. The green is a blind plug, in the yellow one was made a filter hole. Inserting to the ear a suitable end of the earplug gives a possi- bility to transmit a sound wave through the filter or it totally cuts it off. These earplugs are made in one size that fits most". The third generation of plugs CAE www.fragoutmag.com