Olin College of Engineering - Designing and Building an OAE Device 

Odalys Benitez 

OAEs allow for noninvasive hearing screening, only measuring ear characteristics — no user feedback needed, perfect for infants.

For my senior engineering capstone, I worked with a team of Olin and Babson students to figure out how we can build an OAE device from scratch, and distribute it in Latin America.
Infant hearing impairments are often overlooked, especially in underresourced organizations that can't afford the equipment to provide hearing screenings. This is a major problem because an estimated 60% of hearing loss is preventable and can be treated if it is caught soon enough. Those with undiagnosed hearing loss can be perceived as dumb and face discrimination because of their delayed language development. The cost of hearing screening (OAE) devices is large, going for as much as $4000 in the market, even without additional functionality necessary for practical use. This makes OAE devices inaccessible, especially in the area of our study, Latin America.


Final test bench

As the only one on my team with some amount of electrical engineering experience (not much!), I took the lead on figuring out how to successfully create an OAE device prototype. We were in a unique position because we could reference OAE documentation and tech development from expired patents to build the device. OAE-based hearing screening requires two speakers and a microphone. The two speakers each play a different pure tone (which we'll call f1 & f2), which causes our inner ear mechanism's hair cells to vibrate at a corresponding frequency found at (2*f1 - f2). This responding frequency is known as a "distortion product". I worked on amplifying our microphone's signal, running it through a bandpass filter to reduce surrounding noise, and obtaining FFTs to determine if our OAE probe was actually receiving a distortion product. I also created a PCB adapter to hold our amplification circuit and minimize the distance of tedious and fragile enamel wires. By the end of the capstone, we received our first distortion product. To welcome the next capstone team into the next phase of development, I built a test bench to hold the circuit.

A bandpass filter and amplifier used to isolate the distortion products.
The frequency response from a healthy ear. The peak towards the left is the ear's frequency response!
One of the professors testing the system
PCB of the microphone adapter

Short introduction to our project