A crying baby. A chatty couple. Engines spinning. You may be scrambling for headphones when your flight gets noisy – but this experiment by Dr. Darren Hartl aims to take the concept to new heights.
Dr. Hartl, an associate professor of aerospace engineering, and aerospace engineering Ph.D. student Kevin Lieb lead the experiment to develop a unique instrument: a device that can detect visually where a sound is coming from, or in other words: ‘see sound’.
It’s anything but your average aerospace experiment – but the results could have a major impact on commercial and military airplanes.
Previous tests of the acoustic imaging instrument used an airplane wing in a wind tunnel to begin tracking single sounds and noises – but their newest test is far more engaging. Dr. Hartl and Lieb decided to call upon a small section of The Century Singers, a 100-member concert choir of talented men and women. It’s the second-oldest choral ensemble at Texas A&M.
“The sounds from the previous tests could be boring, so we decided to test the instrument in a more right-brained way,” said Hartl.
The students then sang in front of the instrument, allowing Hartl, Lieb, and their team to see their voices. The student-built instrument uses software that allows it to capture every note.
“This experiment allowed us to explore more of the instrument’s capabilities, as opposed to answering a specific research question,” said Hartl.
The instrument was compared with an off-the-shelf acoustic imaging system. While the off-the-shelf model provides near-instant results, the model created for the experiment uses more microphones, allowing the team to more accurately detect where sounds are coming from.
As you may have guessed, when the acoustic instrument is put into practice, its goal is to detect where sound is coming from in-flight to make airplanes quieter. Sounds come from many different places on an airplane, and while they’re not always as easy to stop as a beeping wristwatch, the instrument is an essential first step.
“With techniques like this, we’re able to look at the plane and not just ask ‘is it loud?’, but ‘why is it loud?’” said Lieb. “We can address where a sound is coming from, and what we can do about it, which makes this a really cool diagnostic technique.”
Aside from comfort, a quieter airplane means improved focus for pilots, whether it’s a covert military operation or an outbound flight from Easterwood Airport. Controlling plane noise can help as city congestion continues, and more homes are built near airports.
“If you’ve ever flown, you may notice that you take off and then all of a sudden it feels like the thrust falls off once you’re in the air. That’s a noise control regulation. Pilots have to cut back, so the planes don’t expose neighborhoods too loud of sound,” Lieb said. “Anything we can do to reduce aircraft noise is good.”
Hartl and Lieb have collaborated since Lieb’s freshman year at Texas A&M.
“When I sent out an advertisement to the photography club for a student to take photographs of experiments, who would answer the call but a 4.0 aerospace engineering student, another cool right-brain connection,” said Hartl.
“Kevin is incredibly talented, and I’m very fortunate to get to work with him. He is a leading researcher in this country, and he’s setting himself up to be a national resource when he graduates.”
The experiment also provided Hari Vasudevan, a freshman engineering student and singer, with a new and unique perspective. It shows the interplay between right- and left-brain thinking – the combination of singing with science.
“The experiment gives an insight into sound that we don’t usually think about,” said Vasudevan. “When we sing, we mostly listen to each other to make corrections. Looking at the science of sound using these sensors gives us additional insight about our voices and ways we can improve.”
