Real-world performance of headset active noise reduction systems

Abstract

Active noise reduction (ANR) in headsets promotes the electro-acoustic cancellation of sound within the ear cups of a hearing protector. Operating at frequencies below 1000 Hz, ANR augments attenuation where passive protection is minimal. Personal ANR can reduce the potential for hazardous noise exposure and can facilitate auditory communications. ANR system performance has been characterized to assist purchasing departments in making informed decisions about commercial devices suitable for use in high-noise environments such as helicopters and tracked vehicles. Test methods were developed to assess: (a) active attenuation properties, (b) issues of fitting integrity, (c) speech discrimination performance, (d) saturation or overload threshold limit, and (e) general suitability for long-term use. When properly designed and applied, personal ANR can enhance the listening environment for the user. Nonetheless, performance limitations have been identified in certain devices. Some tended to overload easily or to cease operating under adverse conditions, and others became unstable when the seal around the ear was broken. Proper fitting is pivotal to satisfactory ANR operation, particularly in units with low overload tolerance. Ultimately, the function of any ANR system must be understood in relation to its intended operating environment.