Heyser Memorial Lecture
AES 126th Convention
M,O,C, - Munich, Germany
Thursday, May 7, 2009, 18:30 — 19:30
by Gunnar Rasmussen
Gunnar Rasmussen is a pioneer in the construction of acoustic instrumentation, particularly of microphones, transducers, and vibration-related devices. He was employed at Brüel & Kjær Denmark as an electronics engineer immediately after his graduation in 1950. After holding various positions in development, testing, and quality control, he spent one year in the United States working for Brüel & Kjær in sales and service.
After his return to Denmark in the mid-1950s he began the development of a new measurement microphone with superior long-term mechanical and temperature stability. The resulting one-inch pressure microphone soon became the de facto standard microphone for acoustical measurements, replacing the famous W.E. 640AA standardized microphone.
The optimized mechanical design of the new generation of measurement microphones opened up the possibility for reducing the size of the microphones, first to a 1⁄2” microphone and then to 1⁄4” and 1/8” microphones with essentially the same superior long-term mechanical and temperature stability. Notably the 1⁄2” microphone is still the most widely used measurement tool today. Since the beginning of the 1960s this microphone design has been preferred for all types of acoustic measurements and has formed the basis for the IEC 1094 series of international standards for measurement microphones.
Gunnar Rasmussen received the Danish Design Award in 1969 for his novel design of the microphones exhibited at New York’s Museum of Modern Art. He also developed the first acoustically optimized sound level meter, where the shape of the body was designed to minimize the effect of reflections from the casing to the microphone. This type 2203 sound-level meter was for many years seen as the archetype of sound level meters, and its characteristic shape became the symbol of a sound-level meter.
His other major inventions and designs include the Delta Shear accelerometer, the dual-piston pistonphone calibrator for precision calibration, the face-to-face sound intensity probe, and hydrophones. Gunnar Rasmussen is also the author of numerous papers on acoustics and vibration and has served as chairman and vice-chairman of various international organizations and standard committees. In 1990 he received the CETIM medal for his contribution to the field of intensity techniques. He is also a Fellow of the Acoustical Society of America.
In 1994 Gunnar Rasmussen started his own company, G.R.A.S. Sound and Vibration, a company specializing in precision outdoor microphones for permanent noise monitoring around airports. It is now one of the world’s leading companies in acoustic front-ends and transducers incorporated into a wide range of general purpose and specialized microphones, electroacoustic measurement devices such as ear couplers, precision calibration tools, and multidimensional sound-intensity probes.
The presentation will be followed by a reception hosted by the AES Technical Council.