Method to Streamline, Accelerate the Process of Measuring Acoustics

Newswise — Ning Xiang, chair of the graduate program in architectural acoustics at Rensselaer Polytechnic Institute, has developed a new technique to streamline and expedite the process of measuring acoustics, which can be used to calculate previously unattainable measurements of sound propagation. The research was done in collaboration with John Daigle, an electrical engineering professor from the University of Mississippi.

Using the technique, the acoustical information of any given space can be gathered in mere minutes, allowing for the rapid study and characterization of the acoustics in concert halls and similar performance venues, according to Xiang. The method also can be used as a tool to quickly identify and correct acoustic mistakes within existing venues, or to verify design goals in new building construction.

To measure how sound travels in an environment, an acoustician must position numerous speakers and receivers around the location, to determine how sound moves from every angle of the space. Using the traditional testing method, the acoustician emits sound from one speaker at a time, calculating the speed at which the sound travels to the receiver, as well as documenting changes in the sound's properties such as pitch and volume.

The traditional method of measurement is time consuming, and it is impossible to gather accurate outdoor sound propagation measurements, because wind, temperature, and various other environmental factors that affect sound travel are likely to change multiple times over the lengthy duration of testing, Xiang says. These environmental changes skew test results, rendering them inaccurate and essentially useless, according to Xiang.

Xiang notes that his method, called the simultaneous multiple acoustics measurement technique, makes precise measurements of outdoor sound propagation possible for the first time. "The simultaneous multiple acoustics measurement technique enables all speakers in an area to emit a sound to designated receivers simultaneously, thus compacting the once lengthy measurement process into one short time period," says Xiang. "This is particularly beneficial for researchers who need to collect outdoor sound data rapidly, before environmental factors have time to change."

To interpret the data of each sound as it travels from speaker to receiver, Xiang and his co-researcher have created a new deconvolution algorithm that is loaded onto a computer with data acquisition and digital-to-analog capabilities. The system measures and graphs how well the sounds move within the space.

"The fundamental roots of the simultaneous sound measurement method can be traced back to techniques used in the telecommunications industry," says Xiang. "This is the first time the concept has ever been applied in the acoustics community, where sound tracking problems can often be more challenging than those found in telecommunications."

The significant time-saving benefit of the simultaneous multiple acoustics measurement technique makes it possible to study acoustics in applications that were previously not viable. In addition to outdoor sound propagation measurement, the new method will allow researchers to study such complex systems as the directional characteristics of the human hearing system, the distribution properties of objects that scatter sound (such as acoustic panels), and the acoustic capabilities of various performing art spaces, according to Xiang.

"With further development, the technique will allow researchers to test the sound transfer characteristics of the human ear," says Xiang. "This type of measurement is not possible using the traditional testing method because a person cannot be expected to sit motionless for several hours while multiple speakers positioned around the room are tested individually."

Xiang has been invited to discuss the simultaneous multiple acoustics measurement technique at the Acoustical Society of America and Institute of Noise Control Engineering conference, where he will be presenting an invited paper on his research. The presentation, titled "Maximum-length-related sequences and a specialized deconvolution for multiple acoustic channel estimation," is scheduled for Thursday, Oct. 20 at 4:30 p.m. in the Ramsey Room of the Minneapolis Hilton Hotel, (1001 Marquette Avenue South, Minneapolis, Minn.)

About the Architectural Acoustics Program at RensselaerThe Graduate Program in Architectural Acoustics offers an intense curriculum in acoustics for effectively shaping sonic environments to achieve optimum acoustic performance and sound quality. The program offers studies toward both master of science and Ph.D. degrees. Further doctoral degree studies offer a program in architectural acoustics, providing the knowledge for next-generation acousticians involved in room acoustics, psychoacoustics, acoustic and vibration measurement techniques, and sound reinforcement. The program offers the knowledge and skills needed for advanced practice and applied research. Field work develops the experience of sound environments and musical performance, and industry relations give access to advanced techniques and materials used in acoustical practice.

About RensselaerRensselaer Polytechnic Institute, founded in 1824, is the nation's oldest technological university. The university offers bachelor's, master's, and doctoral degrees in engineering, the sciences, information technology, architecture, management, and the humanities and social sciences. Institute programs serve undergraduates, graduate students, and working professionals around the world. Rensselaer faculty are known for pre-eminence in research conducted in a wide range of fields, with particular emphasis in biotechnology, nanotechnology, information technology, and the media arts and technology. The Institute is well known for its success in the transfer of technology from the laboratory to the marketplace so that new discoveries and inventions benefit human life, protect the environment, and strengthen economic development.