IN-NOVA · Active reduction of noise transmitted into and from enclosures through encapsulated structures

Active reduction of noise transmitted into and from enclosures through encapsulated structures

The European Environment Agency alarms that noise pollution is a major environmental health problem in Europe. More than 125 million people are affected by noise levels greater than 55 dB. In Europe, noise pollution causes 43 000 hospital admissions per year and at least 10 000 cases of premature death per year. People are becoming aware of the negative consequences of prolonged exposure to noise and more often seek to reduce it. Unfortunately, this has not yet been solved, and still requires high efforts. The main goal of the IN-NOVA project is to develop the noise-reducing methods by training 13 Doctoral Candidates through intersectoral, multidisciplinary and international joint research. Scientific objectives of IN-NOVA project are based on a precisely targeted dual noise problem, related to the transmission of noise into and from enclosures through encapsulated structures that concern a vast majority of the population and this can be divided into the two key objectives: 1. Develop comprehensive noise-reducing casing solutions that globally control the excessive noise generated and radiated by industrial devices and household appliances, whilst consuming much less energy, sensors and actuators than classical Active Noise Control (ANC) systems. This is referred to as the in-out problem. 2. Develop versatile active/passive control techniques for the reduction of noise transmission into enclosures, as represented by vehicle and aircraft cabins. This is referred to as the out-in problem. The first of the considered techniques is called the active noise-reducing casing method (in-out problem). The idea is to enclose the noise generating device in an additional thin-walled casing or to use the casing of the device, and make its walls vibrate by using small-size piezoelectric or electrodynamic exciters. The control system provides signals to drive the exciters and change the structural properties of the casing in order to acoustically isolate the device inside (effectively block the noise using the casing). When appropriately implemented, this method results in a global reduction of noise. The second main concept for creating active acoustic barriers has been applied with high performance to vehicle cabins and other small enclosures (out-in problem). The sound field in small spaces can be controlled by using vibration exciters or loudspeakers to generate a secondary field that has a similar amplitude but opposite phase to an unwanted noise field and thus results in noise reduction through destructive interference. Thus, in the vehicle application, this protects the passengers from the noise generated by the engine and the tyre-road interaction.

Data: CORDIS, © European Union