Engineers are developing knee listening device

Research engineers at the Georgia Institute of Technology are developing a knee band with microphones and vibration sensors to listen to and measure the sounds inside the joint.

It could lead to a future device to help orthopedic specialists assess damage after an injury and track the progress of recovery.


Omer Inan has suffered knee pain himself and had been thinking about developing such a device for some time. The assistant professor of electrical and computer engineering is a former discus thrower who was a three-time NCAA All-American at Stanford University and the school record holder.

He spent years whirling around like a tornado, which knees aren’t built for. Add to that the stress and strain of weight training that included squats with 500-pound loads.

“I would always feel like my knee was creaking or popping more if I was putting more stress on it,” Inan said.

Then the Defense Advanced Research Projects Agency (DARPA) issued a call for research proposals on wearable technologies for assisting rehabilitation, and the researcher at the School of Electrical and Computer Engineering pitched his idea.

Inan’s group has published a paper on the latest state of development in the journal IEEE Transactions in Biomedical Engineering online, official print publication is pending. The research is being sponsored by the DARPA Biological Technologies Office. Inan leads a team of 17 researchers, including Georgia Tech faculty in ECE and Applied Physiology and graduate students.

The researchers combined microphones with piezoelectric film. The film is a hypersensitive vibration sensor and collects the best sound, but it is very sensitive to interference. The microphones placed against the skin make for an ample backup and for a more practical device.

The knee monitor also takes advantage of a technical advancement you will find in your smart phone. Micro-electromechanical systems microphones, or MEMS, integrate better with current technology than microphones based on previous technologies, and that also makes the microphones downright cheap – 50 cents to a dollar – for a very affordable device.

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