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University of Alabama's Acoustic Sensor to Reduce Sensing Footprint
Sean Snyder, Associate Editor -- Design News, November 27, 2007
Listen to a about the University of Alabama's new acoustic sensor.
In a case of disaster recovery, a new acoustic sensor being developed at the University of Alabama could aid rescuers in finding buried victims.
“The goal is to develop a sensor that will not only detect a sound, but tell you what direction a sound is coming from and hopefully tell you how far away that sound source is located,” says Dr. Steve Shepard, associate professor in mechanical engineering at the University of Alabama.
Shepard and the University of Alabama recently received a grant from the National Science Foundation (NSF) of $120,000 to develop the device. Once developed, the sensor could replace existing acoustic monitoring methods, which use multiple microphone arrays. “The sound wave will come through and it will hit microphones at different times, and based on that and the phasing information you can infer from what direction the sound is coming, but those usually require a large footprint,” Shepard says. “What we’re hoping to do is develop a single sensor that’s more compact than that.”
The proposed sensor will be a continuous sensor that will use inverse methods like force reconstruction in order to determine the input based on the output. “We’ve developed some techniques where we can look at reconstructing forces that are redistributed over some region of the structure,” says Shepard. “We’re planning to extend that to the case where you would have an acoustic pressure acting on a structure, then measuring the response of the structure and being able to back out what acoustic pressure generated that response,” says Shepard.
One tool to be used in the development and testing of this acoustic sensor is the University of Alabama’s hemi-anechoic chamber, which is a room completely isolated from outside sound. The walls are constructed with 8 inches of metal and a thick layer of sound proofing and diffusion foam. The concrete exterior of the building the chamber is in is 18 inches thick and the concrete floor of the chamber is supported by springs to further eliminate outside vibration.
“The hemi-anechoic chamber will allow us to produce a known acoustic field and it will allow us to reproduce that field as many times as we need to test either one sensor in multiple arrangements or to test multiple sensors,” says Shepard. “If we have two- or three-sensor configurations, we can test each of those in the same duplicate environment to be able to compare the performance of those different configurations.”
The timeline for development of this acoustic sensor is about two years. Tuskegee University will help with the modeling and prototype testing of the sensor. Other applications of the acoustic sensor will include security and military uses.
Dr. Steve Shepard at the University of Alabama is developing a new acoustic sensor under a two year grant from the NSF. Here Shepard talks with Design News about the design process and the use of the University’s hemi anechoic chamber.
