Research Topics: Acoustics, Audio and Electroacoustics, Digital Signal Processing as it applies to audio; Diffraction and Radiation of sound by loudspeakers; Electro-acoustic Measurement Techniques.
Present Research Activities: Active acoustic absorbers, Noise measurements of Wind Turbines, the Acoustics of the trumpet. There is always an interest in measurement techniques
Measurement systems of various types normally work satisfactory when the system under test is truly linear, but nonlinearities can show up surprising differences. Maximum-length sequence (MLS), swept-tone and pulse systems are under study for the characterizations of transducers and acoustic spaces. As well as experiments, computer simulations are used which allow better control of the nonlinearities.
The diffraction of sound by loudspeaker cabinets has been studied with a view to producing simple predictive methods for the effect of a box. A computer algorithm has been applied to solve the Helmholtz sound equation for various shapes, and theoretical analyses show some asymptotic results that are in general agreement with experiment. Currently the diffraction from cabinet edges is under study. The geometrical theory of diffraction is easily modelled on a computer and is efficient enough that second-order diffraction effects can be included. Low-frequency asymptotic results are being used to correct near-field measurements.
Digital Signal Processing is done in our group with an express emphasis on acoustics and audio. Projects include band splitting for multi-way transducers, active noise cancellation, and measurement systems.
Some significant past papers
U.P. Svensson, R.I. Anderson, J. Vanderkooy. Analytical Time-Domain Model of Edge Diffraction, in Proceedings of NAM98, Nordic Acoustical Meeting, Stockholm, Sweden, September 7-9, 269-272 (1998).
Nonlinearities in Loudspeaker Ports, Presented at 104th AES Convention, Amsterdam, May 16-19, 1998. Preprint 4748, 32 pages.
U.P. Svensson, R.I. Anderson, J. Vanderkooy. A Time-Domain Model of Edge Diffraction Based on the Exact Biot-Tolstoy Solution, in the Technical Report of the Institute of Electronics, Information and Communication Engineers, EA97-39, Tokyo, Japan, September 26, 9-16 (1997).
J. Vanderkooy. Aspects of MLS Measuring Systems. J. Audio Eng. Soc. 42, 219-231. (1994)
S.P. Lipshitz, R.A. Wannamaker and J. Vanderkooy. Quantization and Dither: A Theoretical Survey. J. Audio Eng. Soc. 40, 355-375. (1992)
S.P. Lipshitz, J. Vanderkooy and R.A. Wannamaker. Minimally-audible noise shaping. J. Audio Eng. Soc. 39, 836-852. J. (1991)
Vanderkooy. 1991. A simple theory of cabinet edge diffraction. J. Audio Eng. Soc. 39, 923- 933.
J. Vanderkooy and S.P. Lipshitz. 1990. Uses and abuses of the energy-time curve. J. Audio Eng. Soc. 38, 819-836.