News Releases

January 2007

Successful test campaign on the VASCO demonstrator

During the autumn, the Active Control and Experimental Vibro-Accoustics Unit (CAV) directed by Florence Roudolff carried out a two-week test campaign at the Toulouse center within the framework of work aimed at reducing the noise in a helicopter cabin by active control of a composite lining panel passively optimized. This 1.16 m x 1.24 m panel was put under mechanical floor of the VASCO demonstrator, representing a helicopter cabin made of composite, in this instance a NH90 cabin. It was equipped with 13 actuators, i.e. piezo-electric contacts, one in the center and the others arranged around it, and excited mechanically. "Contrary to the test campaign carried out in 2001 during which accelerometers were chosen as sensors, this time we opted for two microphones. In addition, we implemented what is known as MIMO (Multi Input Multi Output), a solution where each sensor can interact with all of the actuators", they specified at Onera. Previously, during the 2001 flight tests, the engineers had used multi-SISO or multi-Single Input Single Output where each sensor only interacts with its actuator.

The results obtained were particularly encouraging. In the frequency bands around 300 Hz, the reductions in acoustic levels obtained were actually between 2 to 3 dB (RMS value). During a later campaign, carried out in the laboratory, between an anechoic chamber and a reverberating chamber, with five microphones placed in front of the panel, one in the center and the four others at the edges, the acoustic level was reduced by 7 dB (RMS value) and by 10 dB on average over large parts of the spectrum. A new test campaign, organized within the framework of a European project, should take place next January.

Composite panel with its piezo-electric actuators

Example of reductions in acoustic levelsl in large frequency band
(20 cm from the panel)

Last Update: 23 January 2007 - © ONERA 2009 - Terms of use