Joshua W.R. Meggitt

Joshua W.R. Meggitt
University of Salford · Acoustics Research Centre

PhD
Looking for collaborative research opportunities in vibro-acoustics and structural dynamics.

About

41
Publications
13,080
Reads
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223
Citations
Introduction
My research interests include: developing improved methods for the characterisation (and assembly) of vibro-acoustic components; the integration of experimental and computational methods; and the treatment of uncertainty in experimental vibro-acoustics.
Additional affiliations
December 2016 - June 2019
University of Salford
Position
  • Research Associate
Description
  • Working on the EPSRC funded project EMBED. For more details follow the link below: http://gow.epsrc.ac.uk/NGBOViewGrant.aspx?GrantRef=EP/P005489/1
October 2014 - January 2016
University of Salford
Position
  • Research Assistant
Description
  • Working on the InnovateUK funded project HVAP. https://gtr.ukri.org/projects?ref=101887
Education
September 2013 - June 2017
University of Salford
Field of study
  • Acoustics
September 2010 - June 2013
University of Salford
Field of study
  • Acoustics

Publications

Publications (41)
Article
Full-text available
Transfer Path Analysis (TPA) is a test-based methodology used to analyse the propagation of noise and vibration in complex systems. In this paper we present a covariance based framework for the propagation of experimental uncertainty in classical, blocked force, and component-based TPA procedures. The presence of both complex and correlated uncerta...
Article
Full-text available
Conventional model updating methods are based on frequency response functions (FRFs) and/or modal parameters estimates obtained from freely suspended, or sometimes rigidly constrained, sub-structures. These idealised boundary conditions are however often difficult to realise in a practical scenario. Furthermore, they are in conflict with the requir...
Article
Full-text available
In-situ Transfer Path Analysis is a diagnostic method used to analyse the propagation of noise and vibration through complex built-up structures. Its defining feature is the invariant characterisation of an assembly's active components (i.e. vibration sources) by their blocked forces. This invariant characterisation enables the downstream structura...
Article
Full-text available
To accurately model the dynamics of a complex built-up structure it is often necessary to forgo the assumption of ideal rigid coupling between components. The dynamic behaviour of inter-component connections, or joints, can have a significant impact on the performance, even survivability, of an assembled structure. For complex structures, where man...
Article
Full-text available
The dynamic properties of joints, or inter-component connections, are a principal source of uncertainty when modelling complex built-up structures. In the present paper, we propose an interval-based sensitivity analysis (SA) to establish the contribution, or influence, of a structure's uncertain joint dynamics towards the uncertainty of its coupled...
Conference Paper
Full-text available
The paper outlines some major developments in Virtual Acoustic prototyping. The story starts in the 1980s (four decades ago) when the prediction accuracy for structure-borne sound of 40 dB (four decades) was considered normal! The group's key innovation has been in describing sources in terms of 'blocked forces' which not only can be measured in-si...
Technical Report
Full-text available
Blocked forces have become an increasingly popular means of characterising the operational behaviour of vibrating machines (such as pumps, engines, gearboxes, electric motors, etc.). Nevertheless, their characterisation and application remains somewhat inaccessible, often requiring many years of experience to master. This document intends to provi...
Conference Paper
There are numerous methods for characterising sound insulating and impact noise reducing compo-nents and systems, each with their own advantages and disadvantages. Two of the predominant mod-elling techniques for prediction of transmission loss through partitions are finite element analysis (FEA)and the transfer matrix method (TMM). FEA has the adv...
Article
Full-text available
In noise and vibration engineering, a structure’s passive dynamic properties are often quantified by frequency response functions (FRFs). This paper focuses on acquiring FRFs from experimental tests, considering both, translational (x, y, z) and rotational (e.g. moments around these axes) terms. In practical applications, test structures may not al...
Article
Full-text available
The purpose of this paper is to present a case study whereby a hybrid experimental-numerical model is used to analyse the structure-borne radiation from a domestic product (vacuum cleaner head). The passive (including radiative) properties of the structure considered are modelled using the Hybrid FE-SEA method. The product's operational activity, w...
Article
Full-text available
The vibro-acoustic analysis of complex structures over a broadband frequency range is an extremely challenging problem that may often require the use of a hybrid deterministic-statistical approach. Due to manufacturing imperfections, the frequency response functions (FRFs) of an ensemble of nominally identical systems can be considered to be random...
Conference Paper
Full-text available
Modern manufacturers usually need to know at a design stage if their products will meet certain vibro-acoustic requirements. In many cases the use of physical prototyping becomes significantly expensive, and engineers opt for the development of predictive computational models. In these cases, a hybrid deterministic-statistical approach can overcome...
Conference Paper
Full-text available
In-situ Transfer Path Analysis (TPA) is a diagnostic method used to analyse the propagation of noise and vibration through complex built-up structures. Its defining feature is the independent characterisation of an assembly's vibratory source in terms of its blocked force, an invariant property that is unchanged by the dynamics of neighbouring comp...
Conference Paper
There is a clear need in modern industries for models that can predict the vibro-acoustic response of their manufactured products at the design stage. Models based on the hybrid deterministic-statistical method are a suitable solution to overcome the challenge of predicting the response of complex built-up systems in the mid-frequency range. Despit...
Article
Full-text available
Blocked forces can be used to describe, independently, the operational characteristics of a vibratory source. Their use within a computational model avoids the need to represent explicitly the complex mechanisms that lead to vibratory excitation. To obtain and apply an experimental blocked force with confidence it is important that likely sources o...
Article
Full-text available
Dynamic sub-structuring (DS) is the procedure by which the passive properties (i.e. frequency response functions) of an assembled structure are predicted from those of its constituent sub-structures. In this paper we are concerned with the propagation of correlated uncertainty through such a prediction. In this work a first-order covariance based p...
Article
A major challenge in automotive NVH engineering is to approach complex structure-borne sound and vibration problems with sufficient accuracy but reasonable experimental effort. Typical issues encountered are poor correlation between objective component performance criteria tested for during bench validation and corresponding subjective targets eval...
Article
Full-text available
Transfer path analysis (TPA) has become a widely used diagnostic technique in the automotive and other sectors. In classic TPA, a two-stage measurement is conducted including operational and frequency response function (FRF) phases from which the contribution of various excitations to a target quantity, typically cabin sound pressure, are determine...
Article
The vibro-acoustic response of complex structures with uncertain properties is a problem of great concern for modern industries. In recent years, much research has been devoted to the prediction of this response in the mid-frequency range where, because neither finite element analysis nor statistical energy analysis are appropriate, a hybrid determ...
Article
Modern industries usually need to ensure that their manufactured products meet certain vibro-acoustic requirements. Therefore, they have a clear need for models that can predict the broadband dynamic response of structural components at the design stage. The use of a hybrid deterministic-statistical formulation has been shown to be a suitable solut...
Article
Full-text available
Inverse problems are widely encountered in fields as diverse as physics, geophysics, engineering and finance. In the present paper, a covariance based framework for the estimation of their uncertainty is presented and applied to the problem of inverse force identification. A key step in its application involves the propagation of frequency response...
Article
Full-text available
This paper is concerned with the development of an experimental method capable of independently characterising low Mach number, in-duct fluid machines, such as pumps, fans, etc. The aim is to propose and test a source characterisation method that is suitable for acoustic simulation and the construction Virtual Acoustic Prototypes. Such a requiremen...
Article
Full-text available
Frequency response functions (FRFs) are routinely used within experimental structural dynamics, among other fields. The uncertainty associated with their measurement is typically modelled on the simplified assumption that additive uncorrelated noise is present. This treatment of FRF uncertainty is questioned here by demonstrating that the notion of...
Article
Full-text available
The context of this paper is the increasing need for vibro-acoustic simulation across many sectors. A procedure is derived for decoupling the components of resiliently mounted assemblies. An independent characterisation of the components is obtained such that they can be mathematically recombined with other elements to form virtual assemblies or Vi...
Conference Paper
Full-text available
This paper is concerned with Shorter and Langley's hybrid method [JSV, 288(3):669-699, 2005] and the incorporation of experimental subsystems. In particular, this paper will address the form of the experimental data required and the procedures necessary to obtain it. Further discussion regarding the theoretical construction of the hybrid model will...
Conference Paper
Full-text available
A crucial step in sub-structuring, vibration source characterisation and transfer path analysis is to correctly define the interfaces between coupled sub-structures. In particular, it is necessary to identify the degrees of freedom through which coupling occurs. Even for experienced engineers, identification of the degrees of freedom required to fu...
Conference Paper
Full-text available
The vibro-acoustic response of complex structures with uncertain properties is a problem of great concern for modern industries. In recent years, much research has been devoted to the prediction of this response in the mid-frequency range where, because neither finite element analysis nor statistical energy analysis are appropriate, a hybrid determ...
Conference Paper
Full-text available
The independent characterisation of a structural component is an essential requirement in many vibro-acoustic problems, including the construction of virtual assemblies and virtual acoustic prototypes. Typically, a complete characterisation involves the determination of both active and passive component properties. This paper concerns the latter, o...
Thesis
Full-text available
A drive towards leaner engineering has seen the use of physical prototypes become a limiting factor in the development of new products. Consequently, alternative prototyping methods are of interest. With their ability to reduce cost, accelerate time to market, and optimize products to higher levels of performance and reliability, virtual methods of...
Chapter
Full-text available
The context of the paper is the need across many industries for prediction and simulation of vibro-acoustic response of assembled structures. One of the main areas of difficulty is to know the excitation forces. The blocked force method allows vibration sources to be characterised independently using conventional measurements similar to those used...
Conference Paper
Full-text available
In the field of experimental vibro-acoustics the ability to predict the response of a coupled assembly from the properties of its constituent parts can prove advantageous, particularly in the development of mechanical goods, such as domestic products, vehicles, and other machinery. A notable example is its use within virtual acoustic prototyping (V...
Conference Paper
Full-text available
This paper concerns the development and application of an in-situ characterisation method for induct sources. Such sources may be attributed to many of the noise problems faced by acoustic engineers, and therefore reliable methods for the analysis and prediction of sound generation and propagation due to induct installations are of interest. Based...
Article
Full-text available
An in situ method for the measurement of a resilient elements dynamic transfer stiffness is outlined and validated. Unlike current methods, the proposed in situ approach allows for the characterisation of a resilient element whilst incorporated into an assembly, and therefore under representative mounting conditions. Potential advantages of the pro...
Conference Paper
Full-text available
During the development of complex assemblies such as aircraft the noise from installed components must be considered. For airborne sound sources this issue has been resolved to some extent by standard measurement procedures which allow equipment suppliers to transfer data to end users in an agreed form. The same cannot be said for structure borne s...
Conference Paper
Full-text available
This paper investigates techniques for auralising continuous broadband sounds both with and without tonal components. This work is part of a wider project to develop a virtual acoustic prototype of a domestic appliance. The ultimate objective is to simulate the acoustic output of the device as a function of its design parameters and operating condi...
Poster
Full-text available
Internal University of Salford conference poster
Conference Paper
Full-text available
An in-situ method for the measurement of a resilient elements dynamic transfer stiffness is outlined and validated. Unlike current methods, the proposed in-situ approach allows for the characterisation of a resilient element whilst incorporated into an assembly, and therefore under representative mounting conditions. Potential advantages of the pro...

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Projects

Projects (3)
Project
The design of products to achieve acceptable levels of noise and vibration is a major concern across a range of industries. In many cases there is a large trade off between cost and performance, and this means that achieving an efficient design is crucial to commercial success. In principle design optimisation can be achieved through testing and improving physical prototypes, but the production of a prototype is time consuming and costly. For this reason there is a pressing need for virtual design methodologies, in which computational models are used to produce a near-final design before a physical prototype is built. Computational models used for noise and vibration analysis must be able to predict the performance of the system over a wide frequency range, potentially ranging from low frequency vibration problems at several hertz to high frequency noise problems at several kilohertz, and this presents severe difficulties. High frequency motions require a very detailed computer model, and this leads to long run times that are not ideal for iterative design. Furthermore, the high frequency performance of a system can be very sensitive to small manufacturing imperfections, and hence the predicted performance may not match the performance of the actual system. These difficulties can be largely overcome by employing recent advances in noise and vibration modelling in which a technique known as Statistical Energy Analysis (SEA) is combined with more conventional analysis methods such as the finite element method (FEM) or the boundary element method (BEM); this approach is known as the Hybrid Method. The Hybrid Method leads to a very large reduction in the run time of the model, while also providing an estimate of the variance in the performance caused by manufacturing imperfections. However, this approach does not fully solve the prediction problem, as a further major difficulty remains: some components in a system can be so complex that it is not possible to produce a detailed computational model of the component, and hence some degree of physical testing is unavoidable. Frequently experimental measurements are used to validate a computational model, or to update the parameters in a computational model, but the requirement here is quite different: the measured data must be used to complete the computational model by coupling a representation of the missing complex component to the other parts of the model. This issue forms the core of the current research project.