NASA Noise-Canceling Vest

Applying audio engineering and elegant design to fit specific use cases...

Primary Skills:

Acoustic Design

Circuit Layout

System Optimization

Max/MSP DSP & Programming

Project Management

As part of the Georgia Tech course "Ubiquitious Computing," we apply user-centered design, wearable, and embedded technologies to solve real problems with companies and organizations from around the world. Through this, I had the opportunity to work directly with NASA to solve an acoustic issue on the International Space Station (ISS).

NASA Design Sketch
Original design sketches of wearable noise canceling vest

More specifically, all of the pumps, fans, and machinery necessary for sustaining life onboard the ISS also create high levels of ambient noise. Rather than relying on passive attentuation that blocks all hearing and communication, NASA was searching for a wearable solution that doesn't occlude the ears and can be tuned to intelligently cancel the unwanted noise. Teamed with a diverse group of GT students with a variety of skills, we set out to solve the technical issue.

Noise Cancellation Theory
Graphic showing the underlying concept of noise cancellation

The complex problem of noise-cancellation is actually fairly simple in theory. Sound is comprised of pressure waves. To cancel an unwanted signal, all you have to do is play back a flipped version of the same signal, or more specifically a phase inverted signal that is called anti-noise. These two signals, when added together, cancel each other through a process called destructive interference. Fortunately, all sound waves are automatically added when they hit the ear drum. Therefore, to cancel noise one just needs to capture a signal, invert the phase, and play it back with as little delay as possible.

NASA System Close-up
Close-up of transducers mounted on 3D-printed collar housing

The result of our iterative design approach entails a wearable vest with a 3D-printed collar to hold transducers near the ear without adding extra bulk, weight, or discomfort. Each ear has one reference mic to capture the ambient noise, one lightweight 1.25" driver to reproduce the generated anti-noise, and an error mic as close to the ear as possible to assess what kind of noise reductions we are achieving. According to NASA, most of the noise is focused in the band between 500 Hz and 2,000 Hz, so transducers and filtering were carefully chosen to optimize performance in this band.

NASA Circuit Layout
Circuit layout for transducer pre & power amplification using TL072 and LM380 IC's

For this project I served as project manager and communicated directly with our contact from NASA to gather their vision of a product, the use cases for the astronauts, and any special design considerations. Additionally, I selected the optimum transducers and created the support circuitry for amplifying the mic and speaker signals, and helped develop the anti-noise algorithm in Max/MSP.

NASA User Testing
Subjective evaluation via user testing and objective testing with a calibrated iOS reference mic

As a team, we performed summative user evaluation combined with objective testing to validate the performance, conmfort, and usability of our design. Overall, participants were able to perceive notable drop in noise levels while not interfering with speech comprehension. These reported drops were supported by differences of up to -10dB as measured by a calibrated reference mic. In April of 2014, we presented our work at the NASA Johnson Space Center Wearable Technology Symposium in Houston, TX.

© Copyright 2014 Riley Winton