Thierry Dubois is a freelance writer specializing in helicopters, business aviation and aerospace technology. He earned a degree in fluid dynamics from an engineering school in Toulouse, France in the mid-1990s. At an unexpected crossroads, he found his first job in journalism. In 1997, he started working for French aerospace weekly Air &amp; Cosmos in Paris. This lasted until 2000, when he moved south to Lyons. He then became a freelancer, working for various aerospace publications and has been part of the AIN team since late 2000. In addition to writing about business aviation, Thierry shares responsibility for the rotorcraft section. He also is a regular on-site writer for AIN’s daily editions at international airshows such as the Paris, Farnborough, Dubai and Singapore shows, as well as at EBACE in Geneva.
In 2007, he won the Honeywell award for “Best systems or technology submission” at the Aerospace journalist of the year awards. In 2013, he won an Aerospace Media Award for the "Best Safety, Training &amp; Simulation Submission."
In other activities, Thierry moderates international conferences on aviation technology topics. Thierry is married and has three children, who seem to begin enjoying the mountains–as their parents do.

Writer

Thierry Dubois

<a href="http://www.ainonline.com/aviation-news/nbaa-convention-news/2011-10-10/e-r-demos-cabin-sound-reality">E-A-R Thermal Acoustics Systems</a> (Stand 2145) is improving acoustic insulation aboard business jets as it endeavors to cut the most annoying cabin noises on a case-by-case basis.


Overall, the best the aviation industry has done so far is focus on the speech interference level (SIL). Manufacturers normally present sound pressure levels, measured in dB at SIL, to indicate how quiet their cabins are. These levels currently are 50 percent lower than they were 10 years ago. However, the dB SIL level in the cabin does not necessarily measure actual acoustic comfort, Brian Joyal, E-A-R’s director of aerospace, defense and rail business, told AIN.


“We are making sound quality better in the cabin by looking at the frequency content of the noise spectrum; it is more than just reducing an overall noise level measured in dBs,” Joyal said.


The noise spectrum is a combination of all noise sources emanating from and around the aircraft. The boundary layer (the air flow on the aircraft’s surface) has a broadband frequency content, while the engines and aircraft systems (fuel and hydraulic pumps, for instance) have rather discrete harmonics. Some actuators also produce discrete harmonics, the noise from which is considered especially annoying. “The frequency content of the noise spectrum is the key to understanding the cabin’s sound quality,” Joyal said.


E-A-R maps the acoustic power flow in the aircraft, and then chooses the right insulation material for the right place. For example, some areas receive structural damping treatment, while other materials act as reflectors of airborne acoustic energy. The U.S. company also has designed mufflers for the air-pressurization system. “Treating noise contributions on a discrete basis helps minimize weight,” he added.


But is good acoustic insulation also good for thermal insulation? “Not necessarily, as acoustic insulation involves a certain amount of air flow, while thermal insulation should be more closed,” Joyal said. Noise insulation is more challenging than thermal insulation, and the company has developed composite blankets with different layers to address these different goals.


The Indianapolis, Indiana-based company’s customers include business jet manufacturers and companies specializing in VIP cabin outfitting, such as Comlux, Amac Aerospace and Lufthansa Technik.

E-A-R Is Cutting Cabin Noise Across The Board

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