Experimental investigation of noise reduction in a flow duct through hybrid passive/active liner

Passive Layer Optimization for Active Absorbers in Flow Duct Applications

“…The design of the hybrid prototype, including the general no flow optimization procedure for our laboratory facility called Matisse and first noise control results have been presented previously in references. [1][2][3] The objective is now to optimize the performances of such hybrid treatments for more realistic applications. In this way, passive and active liner component design processes are carried out separately, independently of each other.…”

A multi-channel feedback algorithm for the development of active liners to reduce noise in flow duct applications

“…A multiple-input/multiple-output (MIMO) control system is therefore necessary to enlarge active surfaces. Digital MIMO ANC feedforward systems proved to be particularly efficient for the control of periodic noise as reported by Galland et al [9] in experiments using a four-cell prototype. Memory requirements and computation loads, however, quickly become limiting factors when, for instance, timevarying periodic noise is being considered.…”

“…Thus, feedback control is preferable. Analogue feedback controllers were developed and tested, but with poor results because their design mainly depended on the electro-acoustic response of each cell (Galland et al [9]). As discrepancies always occur in the manufacturing of the cells, an individual control filter has to be designed for each of them.…”

“…Later, our team applied adaptive algorithms to achieve active control of the real part of the impedance (Furstoss et al [6]). Subsequent studies focused on the development of this technology for flow duct and nacelle applications [9][10][11][12]. Thanks to the double functioning mode of the resulting hybrid cells, the frequency bandwidth over which the efficiency is high is enlarged with respect to conventional passive treatments and purely active technologies.…”