Low-cost, Light-weight, Passive Hearing Protector

Technology #18005

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Professor Nicholas Fang
Department of Mechanical Engineering, MIT
External Link (web.mit.edu)
Jan Xu
Department of Mechanical Engineering, MIT
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Systems, Apparatus, and Methods for Hearing Protection

PCT Patent Application WO 2017-011064


This technology can be used in making passive hearing protection device for personnel working in high-noise operational environments such as

  • aircraft and helicopter cockpits
  • carrier decks
  • weapon training
  • combat
  • mining and metal industry

Problem Addressed

High intensity noise exposure can severely damage hearing. Conventional earplugs attenuate all sound irrespective of frequency reducing operational capability of the person concerned. On the contrary, state-of-the-art active noise canceling circuitry requires additional power supply. The complex design of these noise-canceling headphones leads to higher manufacturing cost compared to the passive devices.


This technology uses acoustic meta-materials to create a passive hearing protection device that can attenuate incoming acoustic pressure waves in specific frequency range. Unlike in traditional passive hearing protection devices,  the acoustic transmission coefficient in the invented design decreases with an increase in the incoming sound pressure level by utilizing a water droplet in the transmitting channel. The enhanced interaction of the acoustic wave and the meta-materials makes the size of the device few centimeters that weighs in tens of grams.


  • Compact size
  • Light weight
  • Low cost
  • No additional power supply