Integrating Piezoelectric Loudspeakers into Aircraft Engines to Reduce Noise

One of the main aircraft engine noises comes from the compression of air between the rotors, mobile parts of the motor, and stators, consisting of static blades. A technology being developed in the framework of a European project, and currently being tested in the Swiss Federal Institute of Technology in Lausanne's Electromagnetics and Acoustics Laboratory (LEMA), aims to integrate piezoelectric speakers into the blades of the stator. They function due to the property of certain materials to deform when an electric voltage is applied. A set of small microphones also placed in the engine captures the incident acoustic wave. They send the information to an electronic controller that calculates the signal to send to each of the loudspeakers integrated into the thirty blades to counter the wave coming from the reactor. "When they work together, the sound of the plane can be reduced by 1.5 to 2 decibel the noise percived by the human ear," notes Hervé Lissek, head of the acoustic group of LEMA.

Transcript

00:00:05 we are now working on activ NSE control technology to reduce aircraft andine noise with different technology such as activ noise control for reducing the fan noise and all these Technologies are developed in the frame of a European project called open air so this is a pizo electric activator a loudspeaker made on p Electric physics so the basic idea is that you have an electrical

00:00:31 voltage that makes it drive the the loud speaker make it move and then this movement is transmitted to the air and creates sounds like a loud speaker here the loud speaker is not creating sound for making sound but for reducing the noise inside the aircraft engine and it creates an nty noise that contacts with the primary sound created by the Rotator interaction parallel to this principle

00:00:56 we have several active control concept developed in open air project uh one is aiming at creating micro Jets to uh interact with the turbulence at the jet exhaust and another concept that is specific to the the lab at tfl is based on using loud speaker as acoustic absorber so we use the membrane of large speakers and we use this membrane to absorb sound energy and to behave as a

00:01:22 sound absorber sound resonator and to have them by electrical control to uh absorb more noise than it does naturally e