NASA Noise Cancelling Vest

NASA needed a unobtrusive wearable device to cancel the machine noise on the International Space Station without interfering with normal everyday tasks and communication. Our team exhibited our working prototype at the NASA Wearable Technology Symposium 2014.

MOTIVATION

  • International Space Station (ISS) has high amounts of ambient noise
  • Potential to damage the hearing of astronauts if they do not have the proper protective equipment
  • There is a need for a protective active noise canceling device that can actively mitigate sounds
  • Must not interfere with the daily activities and motion of the astronaut

OUR APPROACH

  • Goal: Create design and show feasibility as a small drop in noise level
  • System: Wearable noise canceling vest that ISS astronauts can wear during Intra-Vehicular Activities
  • Criteria: Per NASA specification, focus on 500 Hz – 2 kHz frequency range

NOISE CANCELLING PRINCIPLES

  • Out-of-phase signals added together will cancel
  • Acoustic signals are summed at the ear
  • Generate anti-noise to reduce overall noise levels

noise-reduction

PROCESS AND TESTING

  • A cost-effective test system using Max/MSP and a set of stereo desktop speakers
  • Even with uncontrolled acoustic environments and simulated components, we were able to achieve drops in sound levels by over 10 dBA SPL
  • We discovered the system’s ability to reduce noise levels was highly dependent on the environment and position of the user
  • We relied on digital manipulation for the anti-noise processing because of the lack of fine control with purely analog systems

equipment

DESIGN

  • The prototype vest is sized for 50th percentile men with large arm openings for easy movement and any type of shirt underneath
  • 3D printed housing are mounted with thread and velcro, so the back harness can come off if necessary
  • The collar that houses the speakers and mics is as close to the ears as possible without getting in the way of any head gear

design

SYSTEM

  • Two mics and a speaker are mounted on either side of the neck in 3D printed housing
  • The battery and circuitry are on the back of the vest in 3D printed housing
  • The playback level is controlled by a potentiometer on the user’s chest

system

ALGORITHM

  • Adaptive computation based on Least-Mean Squares algorithm in Matlab and C – but not real-time
  • Max/MSP for real-time digital signal processing
  • Receives reference signal, filters, and inverts signal with adjustable delay

algorithm2

TESTING AND RESULTS

  • Two desktop speakers were used to simulate multiple types of ambient noise
  • User controls the level of anti-noise and a SPL meter was placed near the user’s ear to track levels
  • We achieved a 10dBA drop with sinusoidal signals, a 3dBA drop with pink noise, and a 2dBA drop with white noise
  • With a 10dBA drop, users perceived about half the volume of noise
  • User testing demonstrated the sensitivity of the system to motion and the slight tight feeling of the harness

results

FUTURE WORK

  • The vest would be made in more sizes and the speakers could be adjustable
  • Future testing will be done to determine the best placement for the speakers and system
  • More advanced types of DSP are needed for crosstalk, feedback, and adaptive filtering.
  • Additionally, the system would benefit from head and posture tracking to adjust the phase relationship as users tilt and move their heads
Date – Spring 2014
Team – Haytham Abutair, Taylor Powell, Alan Zhang, Riley Winton
Skills – Sewing and patternmaking, Ergonomics
Mentor – Professor Clint Zeagler from Georgia Tech