Andrew Stephen Elliott

Andrew Stephen Elliott
University of Salford · Acoustics Research Centre

BSc, MSc, PhD

About

53
Publications
16,263
Reads
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707
Citations
Additional affiliations
September 2009 - present
University of Salford
Position
  • Research Associate

Publications

Publications (53)
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...
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
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
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
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...
Conference Paper
Interior noise is a challenge for Rolling Stock manufacturers in the search for a comfortable travel experience. To achieve interior noise levels respecting customer requirements, it is necessary to allocate noise and vibration targets to the different train equipment. Airborne source characterization is quite standardized in the railway industry b...
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
There are well-established measurement standards for the rating of impact noise reduction provided by floor coverings in relation to structurally transmitted impact noise, e.g. BS EN ISO 10140-3 and ASTM E492 are widely used in Europe and North America Respectively. Standardisation for “in-room” impact noise transmitted by an airborne path is howev...
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
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...
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
Solid Bodied electric guitars typically employ one or more magnetic pickups attached to the guitar body in close proximity to the guitar strings. At low frequencies the amplitude of the vibrating string is typically far greater than vibrations transmitted through the guitar body and it is likely therefore that the output current is largely dominate...
Article
Full-text available
The airborne sound transmission through a building element such as a partition/panel is governed by the sound insulation of the partition, or the resistance the partition provides to the incident sound. Typically the airborne sound insulation of the wall is rated by a single number quantity given as the Sound Reduction Index (SRI) or the Sound Tran...
Article
Airborne sound transmission through building elements or the sound insulation of the building element is usually rated by its Sound Reduction Index (SRI) or the Sound Transmission Class (STC). SRI/STC quantifies the overall sound transfer but gives no information about how the transfer takes place and what are the contributions of different sound t...
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...
Conference Paper
The airborne sound insulation of a partition is measured by relevant parts of ISO 10140 to thereby give a single number quantity Rw-the Sound Reduction Index (SRI). These standard tests however, do not provide any information on how the sound is transferred through the partition or the contribution of the transfer paths involved to the total sound...
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
The sound insulation of a building element is usually rated by relevant parts of ISO 101401 to give a single number quantity Rw - the Sound Reduction Index (SRI). These standard tests however, do not provide any information on how the sound is transferred through such an element or the contribution of the transfer paths involved to the total sound...
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...
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...
Conference Paper
Full-text available
Transfer Path Analysis methods are one of the most widely used techniques for diagnostic testing of structural and airborne sound transmission. Although widely used in the automotive sector, these methods however have not been adopted in the Building Acoustics domain and the paper intends to explore their usability in this context. Commonly used In...
Conference Paper
Full-text available
RESUMEN: Metamateriales acústicos son materiales fabricados artificialmente, los cuales están diseñados con el fin de controlar, direccionar y manipular ondas sonoras. Estos materiales están adquiriendo bastante popularidad debido a que presentan propiedades acústicas que no son comúnmente observadas en materiales convencionales. Entre éstas, se en...
Article
Full-text available
An omnidirectional sound absorber based on the acoustic analogy of the electromagnetic metamaterial “black hole” has been developed and tested. The resulting structure is composed of a hollow cylindrical porous absorbing core and a graded index matching layer which employs multiple rods of varying size and spacing to gradually adjust the impedance...
Article
An expression for the Green's function at an arbitrary set of passive locations (no applied force) is derived and validated by experiment. Three sets of points are involved, the passive reconstruction points, c, which lie on a virtual boundary and two sets of auxiliary points, denoted a and b, located either side. The reconstruction is achieved usi...
Article
Source-path-contribution (SPC) analysis, also known as transfer path analysis (TPA), is a technique widely used in the automotive industry for rank ordering noise and vibration sources. The SPC approach is known to provide reliable diagnostic information but is time consuming to apply. In this paper, a faster SPC approach that allows all measuremen...
Article
Full-text available
An omni-directional acoustic absorber consisting of a porous core and the impedance matching metamaterial layer has been designed and tested in the laboratory. Semi-analytical and numerical models have been developed and validated. The numerical model takes into account the viscous losses in the matching layer. A 1.5 m demonstrator has been built a...
Article
The paper addresses the problem of how to characterize vibration sources and isolators with measurements made in-situ, either on a working installation or on a test bench. For example, automotive components are often characterized by test bench measurements, but there is a need to know how they will behave when coupled to components with potentiall...
Article
Frequency response functions (FRF), such as mobilities, are widely used in the analysis of vibration and structure-borne sound and it is important that this FRF data can be measured accurately for all important degrees of freedom. In some cases three translational and three rotational components of both excitation and response may be of importance;...
Article
Full-text available
Noise continues to be a significant factor in the development of wind energy resources. In the case of building-mounted wind turbines (BMWTs), in addition to the usual airborne sound there is the potential for occupants to be affected by structure-borne sound and vibration transmitted through the building structure. Usual methods for prediction and...
Article
Three relationships are presented for indirect determination of the structural dynamic properties of substructures, namely the blocked force, mobility and free velocity. First, it is shown that the blocked force of a vibration source can be obtained from measurements made in situ, i.e. when the source is connected to a receiver structure. This pote...
Article
A method has been developed to characterize a vibration source when coupled via resilient mounts to a receiver structure. This two-step measurement procedure can deliver the mobility and free velocity of a source, together with the mobility of the receiver to which it is connected, without decoupling the two structures. The method is feasible in a...
Article
A novel method has been outlined in the first part of this paper aimed at characterization of structure-borne sound transmission from a vibration source coupled via resilient mounts to a receiver. It can deliver the source mobility and its free velocity, together with the mobility of the receiver to which the source is connected, without decoupling...
Article
Full-text available
Building mounted micro wind turbines (BMWTs) could potentially provide a useful contribution to renewable energy production but a means of predicting structure-borne sound and vibration is required. A particular difficulty is that BMWTs can only be operated when properly installed, therefore any source characterization measurements must be conducte...
Article
A measurement method is introduced which allows the blocked forces of a structure-borne sound source to be obtained from measurements in situ. The main advantage of the method is that it can be applied to an existing installation without the need for any special test arrangement. It is possible to obtain the 'characteristic power' of the source whi...
Article
It is shown that the blocked force of a structure-borne sound source can be obtained from measurements made in situ, i.e. when the source is connected to a receiver structure. This potentially removes the need for special test rigs employing blocked terminations. A corollary of this relationship is that a theoretically exact ‘in situ transfer path...
Article
Full-text available
Measuring only force mobilities it is possible to derive a moment mobility without the need for an externally applied moment. The method uses finite differences of both forces and velocities about a central point. In this way pure forces and moments can be extracted as can pure velocities and angular velocities. There are, however, errors associate...
Article
Full-text available
In-situ source characterisation methods are those which involve measurements made whilst source and receiver are coupled as they would be in a real installation. Potentially in-situ source characterisation may account for the physical reality lost in the "black box" approach. There are other potential benefits such as ease of measurement. In this w...
Article
Structure-borne power transmission can in theory be predicted using the mobility method. In order to facilitate this one would measure source and receiver mobilities and either the free velocity or blocked force. The subject of this paper is how to obtain this data. Two in-situ methods for source characterisation are outlined and some preliminary v...
Article
Due in part to the difficulties encountered when characterising structure borne sound sources, a potentially significant contributor to overall product noise is often overlooked. A simple useable method for structure borne source characterisation would therefore be very valuable. For structure borne sound a source would generally be characterised b...
Article
An in-situ method has been developed for the characterisation of a vibrating source coupled via resilient mounts to a receiver structure. Using a 2-step measurement procedure the mobilities of the source and the receiver can be identified without decoupling the two structures. The stiffness of the mounts need not be known, the only assumption being...

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Projects

Projects (2)
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.