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Date: Tuesday, November 15, 2011 at 7:00 pm

Speaker: Mark Serridge, Bruel & Kjaer, Shadow Hills, CA

Topic: Measuring the Sound Field Inside a Large Spacecraft Acoustic Test Chamber

Space flight hardware is frequently tested for its vibrational response to the types of high sound pressure levels that might be encountered during the launch stage. The flight hardware is placed in a large reverberant chamber and is exposed to high sound pressure random noise. The vibrational response measured can then be compared to that predicted via a number of standard modeling techniques. These models use the conventional assumption that the sound field inside the test chamber is diffuse. However, this assumption has never been put to the test and unpredicted vibrational responses are not uncommon. In November 2008, a large (50,000- cubicfoot) acoustic test facility was measured and mapped over a period of 3 days. This was done by moving a 100 microphone array throughout the chamber volume while operating the chamber. A three-dimensional sound pressure map was produced, offering a stunning view of something never before seen. The map showed that indeed the sound field was not as diffuse as expected.

Mark Serridge earned his degree in Engineering Acoustics and Vibration from the Institute of Sound & Vibration Research (ISVR) at Southampton University in UK in 1983. He began his career as a loudspeaker engineer at ELAC in London before moving to Bruel & Kjaer in Denmark in 1985. Now, 26 years later, he is still with Bruel & Kjaer where he now manages sales and applications of Bruel & Kjaer products in the Southern California area. He specializes in urban noise monitoring, modal testing and sound intensity. He has published and presented many technical papers in the field of machinery vibration analysis, and advanced acoustic transducers and analysis techniques. His most "famous" work is the 126-page, definitive Bruel & Kjaer text book called Piezoelectric Accelerometers and Vibration Preamplifiers, which he co-authored in 1986 with Torben Licht. That book was eventually translated into 6 different languages. He is also a performing jazz musician and lover of fine food and wine.

Time: 7:00-7:30 pm Coffee and Refreshments

7:30-8:30 pm Meeting

8:30-9:00 pm Coffee and Discussion

Place: Veterans Administration Medical Center, Room 6400 (6th floor)

Wilshire and Sawtelle Boulevards (near 405 freeway)

Parking in front of Medical Center