Former CSL student’s research on inaudible acoustics rewarded with PhD Thesis Award

Former CSL student Nirupam Roy’s inventions on inaudible acoustics and its wide impact on the Internet of Things (IoT) research have earned him the 4^th annual CSL PhD Thesis Award which will be presented later today.

 “Inaudible acoustics sounds like an oxymoron, but we have explored beyond its apparent contradiction,” Roy said.

Roy’s research involves using frequencies above a normal human’s hearing range (20-20,000 hertz) to block, or jam, microphones, preventing unapproved recordings. While these frequencies are normally inaudible to microphones as well, Roy shows how the

nonlinearity of the channel can be exploited to make them audible to microphones.

“Imagine we are having a conversation in a room, but we don’t want this conversation to be recorded with any microphone,” said Roy, currently an assistant professor in computer science at the University of Maryland College Park. “To prevent an eavesdropper from recording our conversation, we could play a loud sound that will mask the conversation, but it will also interfere with the conversation. Using an inaudible sound, we can create an inaudible jammer that can block all microphones in the room but will not interfere with the conversation.”

There are many applications of this type of technology, from shopping malls to museums, it can provide an extra level of privacy and security to conversations. Many researchers are looking at how to improve security, but Roy’s approach is a new take on an old idea, something his adviser Romit Roy Choudhury thinks helped him win the prestigious award.

“Acoustics and vibrations have been classical and mature topics, however, Nirupam shows that revisiting the area through the lens of embedded systems, and IoT, opens new opportunities,” said Roy Choudhury, W.J. "Jerry" Sanders III - Advanced Micro Devices, Inc. Scholar in Electrical and Computer Engineering. “Nirupam’s work opens a space of applications in which regular microphones can be used as an ‘acoustic receiver’ and yet, the acoustic signals themselves would be inaudible to humans.”

Roy was the first to show an inaudible command such as “Alexa, open the garage door,” would trigger an Amazon Echo to respond without anyone hearing the command. This type of application was the focus of a New York Times article, discussing the group’s research. An article discussing their research to combat these types of commands was published by CSL in 2018. His other research includes secure communication methods using inaudible and imperceptible acoustic signals, and the ability to recover human voices from subtle vibrations induced in nearby objects.

It is clear that Roy’s research does and will continue to have an impact, but that’s not the only reason he is the recipient of this year’s CSL PhD Thesis Award. One of the requirements is interdisciplinary, a requirement Roy found easy to achieve within CSL.

“CSL is a place of collaboration. I never hesitated to talk to the faculty and fellow students about my research and always received good feedback and new perspectives on my problems,” said Roy. “I think CSL has become an ideal place for bleeding-edge research that requires interactions of minds from different fields of science.”

As part of receiving the award Roy returned to campus on October 28 to present his thesis research as well as some of his current research that has been an extension of his thesis work. He is both honored to receive the award and excited to return to Champaign, which he calls his second home.

“Accolades are sweetest when it comes from the family,” said Roy of receiving the award. “Since I spent my entire Ph.D. term at CSL, it means a lot to be recognized for my work at CSL. It feels like someone from my family is saying -- good job, Nirupam.”