Acoustic Sensor Being Developed In New Anechoic Chamber

Typically, multiple microphones are used to measure 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.

“It’s exciting to work on a project that could dramatically change the effectiveness of emergency response teams,” said 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. The chamber is a room that is isolated from external sounds. The walls and ceiling are covered with a very-thick, foam-like material that eliminates all acoustic reflections. Shepard stated that being in the chamber is, “like standing in a very large quiet field. You can almost hear your own heartbeat.” This isolation allows for detailed acoustic measurements on a wide range of structures.

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. Additionally, the entire chamber and the 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, another sound barrier.

“This chamber gives UA unique acoustic testing capabilities that most research organizations simply don’t have,” said 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 said there are several areas researchers hope to explore, including:

• reducing noise through powered systems and soundproofing
• health monitoring of machines
• heating and air conditioning system components
• Gear, bearings, motor and engine noise
• Consumer product noise and vibration

Shepard was awarded the $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 to this research project. Throughout the project, UA and Tuskegee faculty and students will have an opportunity to use the chamber to evaluate prototypes for the acoustic sensor.