The University of Alabama

Can You Hear Me Now?

Better Than You Can Imagine with New UA Test Chamber

By Mary Wymer

Human hearing can only discern the location of a noise to a certain level–beyond that we have to rely on technology. Although having the ability to locate a sound source could be vital for emergency location after a disaster, traditional sensors are too cumbersome and difficult to use in such situations.

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Researchers at The University of Alabama are developing a new compact acoustic sensor that will enable users to accurately locate a sound source. In evaluating the performance of this new sensor, researchers will use UA’s new hemi-anechoic chamber.

Typically, measurements from multiple microphones spread out over a large area are used to determine the location of an acoustic source, but this project is aimed at developing a single sensor that performs the same task. Its applications will be useful in aiding the military, homeland security and emergency rescue efforts.

Dr. Steve Shepard in UA’s new test chamber. (Photo by Laura Shill)

Dr. Steve Shepard in UA’s new test chamber. (Photo by Laura Shill)

“It’s exciting to work on a project that could dramatically change the effectiveness of emergency response teams,” says Dr. Steve Shepard, associate professor in mechanical engineering. “For instance, if a building collapses, our sensor could locate the noises made by victims trapped under debris and help rescue those victims more quickly. The sensor could also be used for security purposes, such as monitoring the location and motion of vehicles.”

Once a prototype is developed, the sensor will be tested in UA’s new hemi-anechoic chamber, which is one of the largest in the Southeast.

Visually, the chamber resembles a high-tech recording studio. The chamber walls are covered by 2-foot thick, gray, triangular-shaped foam wedges. The 8-inch thick metal walls are filled with insulation made from recycled denim material. All of this material serves two purposes. First, it prevents any noise from entering the chamber. Second, it eliminates any acoustic reflections from the walls and ceiling inside the chamber. Shepard says that being in the chamber is “like standing in a very large quiet field. You can almost hear your own heart beat.”

The chamber and its supporting concrete floor, all 150,000 pounds, float on springs to prevent outside vibrations from interfering with acoustic testing. The entire chamber is located in the AIME Building, which has 18-inch thick exterior concrete walls that also help reduce outside noise.

“This chamber gives UA unique acoustic testing capabilities that most research organizations simply don’t have,” says Shepard. “This is true particularly when it comes to testing large machines, structures, and even automobiles. We can now take acoustic measurements on a machine and not worry about the effects of reflections or outside noise. Our ability to better understand how that machine radiates noise, and develop ways to make it quieter, has been greatly extended.”

Shepard says there are several areas researchers hope to explore, including reducing noise through soundproofing, health monitoring of machines, heating and air conditioning system components, gear and bearing noise, motor and engine noise, and consumer product noise and vibration.

Shepard was awarded a $120,000 grant from the National Science Foundation to develop the new sensor. UA’s College of Engineering is partnering with Tuskegee University where researchers received an additional $100,000 grant for their contribution. Throughout the project, UA and Tuskegee faculty and students will have an opportunity to use the chamber to evaluate the performance of prototypes for the acoustic sensor.

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