Adaptive noise reduction and speech intelligibility using shape memory metamaterial-based hearing protection earmuffs

Area of Science:

• Materials Science
• Acoustical Engineering
• Occupational Safety

Background:

• Conventional passive earmuffs (SNR 28-32 dB) block hazardous noise but also essential low-intensity sounds like speech.
• This communication barrier leads workers to remove earmuffs, increasing accident risk.
• Pressure level-dependent earmuffs offer a solution by selectively filtering sound based on intensity.

Purpose of the Study:

• To evaluate the speech intelligibility and hearing protection of a novel pressure level-dependent passive earmuff prototype.
• To assess the efficacy of shape memory metamaterial inserts in selective sound filtration.
• To compare user experience with the prototype against commercially available earmuffs.

Main Methods:

• Development of a pressure level-dependent passive earmuff prototype utilizing shape memory metamaterial inserts.
• Controlled environment testing of hearing protection and speech intelligibility.
• Numerical simulations of earmuff components to optimize noise reduction across various sound intensities.

Main Results:

• The prototype maintains an in-ear sound pressure level below 82 dB across frequencies, even with external noise up to 110 dB.
• Fair speech intelligibility was achieved in both quiet and noisy conditions.
• 85% of participants preferred the prototype over conventional earmuffs.

Conclusions:

• The developed shape memory metamaterial earmuffs effectively balance hearing protection with speech communication.
• This technology offers a promising solution for improving safety and usability in noisy work environments.
• User preference data supports the potential adoption of this advanced hearing protection technology.