Noise reduction in a launch vehicle fairing using actively tuned loudspeakers

Abstract

Loudspeakers tuned as optimal acoustic absorbers can significantly reduce damaging, low frequency, reverberant noise in a full-scale launch vehicle fairing. Irregular geometry, changing payloads, and the compliant nature of the fairing hinder effective implementation of a passively tuned loudspeaker. A method of tuning the loudspeaker dynamics in real time is required to meet the application requirements. Through system identification, the dynamics of the enclosure can be identified and used to tune the dynamics of the loudspeaker for reduction of targeted, high intensity, low-frequency modes that dominate the acoustic response in the fairing. A loudspeaker model with desired dynamics serves as the reference model in a control law designed to tune the dynamics of a non-ideal loudspeaker to act as an optimal tuned absorber. Experimental results indicate that a tuned loudspeaker placed in the nose cone of the fairing significantly reduces acoustic energy and verifies results calculated from the simulation.

Implicit coupling methods for nonlinear interactions between a large‐deformable hyperelastic solid and a viscous acoustic fluid of infinite extent

“…In recent years, there has been a widespread upsurge of interest in analyzing nonlinear interactions between large‐deformable elastic structures and acoustic waves. In particular, finite‐amplitude acoustic waves radiated from hyperelastic solids in a fluid of infinite extent have been attracting great attention due to their comprehensive applications in aerospace engineering, 1 biomedical applications, 2 etc. For example, a hyperelastic membrane attached with an acoustic cavity can be used as a broadband sound absorber by taking advantage of the modes of cavity and membrane at the same time 3,4 .…”

Self-learning active noise control

“…3,4 The same condition is required so that the secondary path model is minimum phase for stable operation of active resonators. 5,6 Due to practical restrictions, sensors are placed sufficiently away from actuators and secondary paths are nonminimum phase in many ANC applications. Besides, dynamics of electronic circuits are ignored in the derivation of Eqs.…”

“…Examples of feedback MIANC systems are direct rate feedback controllers or active resonators, which are theoretically stable in sound fields if dynamics of electronic circuits are negligible. [3][4][5][6] In reality, dynamics of electronic circuits are not necessarily negligible and may cause stability problems to direct rate feedback controllers or active resonators. Many direct rate feedback controllers and active resonators require collocated feedback signals.…”