OTTO's New Hurricane III headset with SureFire patented EarLock (R) Retention Rings and Noise-Reducing Filters incorporates ground breaking technology from SureFire, a leader in hearing-protection technology. Sounds at safe levels, including speech, are allowed to pass through and can be clearly heard, while potentially harmful noises are reduced via a proprietary design that incorporates a special Noise-Reducing Filter. A sliding switch allows the user to control ambient sound level, while preserving situational awareness. In the open position, the filters allow ambient sounds and conversations to be heard clearly. In high noise environments, closing the siwtch increases noise blocking effectiveness. Ambient background noise is reduced by 21dB, with up to 40dB of protection against loud noises.