The Virtual Acoustic Room by William Grant Gardner

A room may be used for a wide variety of performances and presentations. Each use places different acoustical requirements on the room. We desire a method of electronically controlling the acoustical properties of a room so that one physical space can accommodate various uses. A virtual acoustic room is a room equipped with speakers, microphones and signal processors that functions as an interactive room simulator. Sounds created in the room are detected by the microphones, processed to simulate a desired acoustical space, and returned to the room via the speakers. In order to ensure stable operation and enable simulation of arbitrary spaces, acoustic feedback from the speakers to the microphones must be canceled. The resulting system is a combination of acoustic feedback cancellation technology and multichannel room reverberation technology. This thesis investigates methods applicable to constructing a virtual acoustic room. Acoustic feedback cancellation using static, finite impulse response (FIR) filters is investigated. This technique involves measuring the speaker to microphone response using pseudo-random noise, and creating an FIR cancellation filter from the resulting room response. Multichannel room reverberation rendering is accomplished by using the source image method to determine the early echo response of the virtual room and simulating the diffuse reverberant response using digital reverberators based on nested and cascaded allpass filters. A single channel realtime acoustic feedback cancellation system and a four channel realtime room simulator were constructed. Thesis Supervisor: Barry Lloyd Vercoe, D.MA. Title: Professor of Media Arts and Sciences This work was supported in part by the Television of Tomorrow Consortium and Pioneer, Incorporated.