A Sound Idea

July 29, 2013 in Technology, Environment

Most people shy away from the irritating noises we can experience during air travel but not Jim Angerer and Dianne McMullin. These Boeing engineers want to know how every creak, crack and whistle affects airline passengers. They collect data from test groups and computer analysis to make recommendations about designing new products and improving the flying experience.

Angerer and McMullin use several methods and testing facilities to evaluate the human reaction to certain sounds. One such facility is the Boeing Test & Evaluation critical listening lab, a room set atop three feet of concrete with an inner and outer wall of concrete blocks. It is home to Angerer and his unique test methods and tools, namely bagpipes and a binaural recording mannequin.

The mannequin may look like something you might use to practice self-defense but special sensors allow it to record sounds while placed in an airplane seat. “It allows us to make recordings in the cabin and replay them in a lab or cabin mockup so the listener hears them as though they are seated in the airplane,” explained Angerer, a test and evaluation engineer. This allows the data to be analyzed and dissected according to the reaction of the listener.

“I’ve heard this demonstration many times before but it still shocks me at how real it is,” said McMullin, a human factors engineer with Boeing Commercial Airplanes.

Another important tool for testing noise is the anechoic chamber. A large room whose name means “no echo” is filled with foam wedges that are designed to absorb and eliminate sound reflections. It is used to measure very specific properties of noise that may radiate from an object. Sound sources are evaluated based on measurements made with microphones in the acoustic free field of this quiet environment.

To put these tools to practice, McMullin used a section of a 767 cabin and converted it into a new 787 interior. Placed along the outside of the fuselage were 28 speakers to simulate the sound of the engines, air rushing passed and the environmental control system. Passenger volunteers were able to experience the sounds of flight while on the ground and evaluate their reaction to them. More importantly, the data collected gives Boeing information that can influence future products and their design.

“This is a decision making tool for engineers to change designs,” said McMullin. “The bottom line is to make passengers comfortable.”