Comparison between subjective and objective measures of active hearing protector and communication headset...

Area of Science:

• Acoustics
• Audiology
• Occupational Safety

Background:

• Communication headsets and hearing protectors with active noise reduction (ANR) are increasingly used.
• Accurate measurement of ANR effectiveness is crucial for protecting hearing and ensuring clear communication.
• Existing measurement methods may be affected by environmental noise and device variability.

Purpose of the Study:

• To develop and evaluate subjective methods for estimating the attenuation of ANR systems.
• To compare these subjective methods with physical insertion loss measurements.
• To assess the impact of ANR system asymmetry on attenuation estimates.

Main Methods:

• Developed masked-threshold and loudness-balance methods for subjective attenuation estimation.
• Conducted measurements in the presence of environmental noise, minimizing subject noise exposure.
• Performed physical insertion loss measurements using a miniature concha microphone for comparison.

Main Results:

• Masked-threshold method overestimated attenuation when ANR differed between left and right earcups.
• Loudness-balance method provided reduced estimates of active attenuation.
• Physical insertion loss measurements showed variability influenced by microphone position and sound field under the earmuff, with differences up to 20 dB at low frequencies.

Conclusions:

• Subjective methods, particularly loudness-balance, offer valuable insights into ANR performance.
• Asymmetry in ANR systems can significantly impact subjective attenuation estimates.
• Physical measurements require careful consideration of microphone placement due to spatial sound field variations under active earmuffs.