Active control of far-field sound power produced by vibrating structures using direct distributed sensing of acoustic radiation modes

Lead Research Organisation: University of Southampton
Department Name: Faculty of Engineering & the Environment

Abstract

Working machinery is a major source of vibration in marine vessels and considerable effort is devoted to developing isolation systems that reduce transmission to the hull. This is partly for improving crew and passenger comfort but, in the case of Naval vessels, it is primarily to suppress the associated acoustic noise and hence reduce the vulnerability to detection by acoustic mines or passive sonar. A particular problem associated with machinery isolation in marine environments is structural resonance. This occurs both in the machinery support structure and in the hull. Such resonance leads to very high forces transmitted across machinery mounts and where resonant frequencies coincide with structural modes of the hull that have high acoustic radiation efficiency, this poses a very significant problem. Although BAE Systems patented Selective Damping technology has been shown to be a highly effective control approach, it is important that new efficient distributed sensor arrays are developed that provide direct information relating to radiated sound power at the fluid/hull interface in order to minimise cost, power and weight.
Moreover a significant contribution to internal and radiated noise in maritime vessels often arises from the excitation of lightly damped panels. Although passive-damping treatments can sometimes provide an effective solution, for many cases the performance can also be limited. This can be due to:
Insufficient damping at low frequency due to practical weight/size constraints.
Acoustic radiation associated with non-resonant forced motion (machinery casing, for example).
Limited options in flood spaces.
As a result an alternative and more widely applicable approach is required that will provide a broadband control capability within a lightweight panel structure. This proposal is for a PhD programme that will address both the requirements described above through the development of a smart multifunctional composite panel (or tile} that incorporates active, semi-active and passive elements within a layered structure.

Publications

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Milton J. (2017) Decentralised active vibration control using a remote sensing strategy in 24th International Congress on Sound and Vibration, ICSV 2017

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Milton J. (2018) An inverse method for the identification of the radiation resistance matrix from measurable acoustic and structural responses in 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509358/1 01/10/2015 30/09/2020
1721765 Studentship EP/N509358/1 26/09/2016 30/09/2020 Joseph John Milton
 
Description I have developed a method for estimating the radiation resistance matrix (the radiation resistance matrix allows the sound power radiated from vibrating structure to be estimated using structural measurements) of a flat plate, using measured structural and acoustic responses when excited by a distribution of independent forces.

I have then validated the method through both simulation and experimental based investigations.

The experimentally identified radiation resistance matrix has then been incorporated into the design of an Active Structural Acoustic Control (ASAC) algorithm, which enables one to control structurally radiated sound power using only a structurally located sensor and actuator arrangement.
Exploitation Route Work on the experimental identification of the radiation resistance matrix will be extended to more complex structures, for example, a cylindrical shell.

Following this, control of the radiated sound power from the structurally excited cylinder will be investigated using the proposed ASAC strategy.

This work will be taken forward by myself over the next 12 months.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Manufacturing, including Industrial Biotechology,Transport

URL https://eprints.soton.ac.uk/id/eprint/422946
 
Description The findings can be used to address current habitability issues with maritime vessels.
Sector Aerospace, Defence and Marine