Adventures in High Intensity Acoustic Testing: a Loudspeaker System for Small-Scale Tests (2023)
Conference Proceeding
Hargreaves, J., Hipperson, J., Wong-McSweeney, D., & O'Doherty, N. (2023). Adventures in High Intensity Acoustic Testing: a Loudspeaker System for Small-Scale Tests.

In the space and aerospace industry, there is a need to perform High Intensity Acoustic Testing (HIAT). This aims to recreate in the laboratory, for the purpose of qualification testing, the extreme acoustic environments that designs must survive in... Read More about Adventures in High Intensity Acoustic Testing: a Loudspeaker System for Small-Scale Tests.

Extending the Low Frequency Acoustic Centre Concept to Directional Loudspeakers (2023)
Conference Proceeding
Hargreaves, J. (2023). Extending the Low Frequency Acoustic Centre Concept to Directional Loudspeakers.

The Acoustic Centre of a loudspeaker is defined as being the point from which spherical waves appear to radiate. This is useful to know when performing phase, level, or time alignment, for example. For a single driver in a sealed box, it is typically... Read More about Extending the Low Frequency Acoustic Centre Concept to Directional Loudspeakers.

A comparison between the high-frequency Boundary Element Method and Surface-Based Geometrical Acoustics (2023)
Journal Article
Hargreaves, J. (2023). A comparison between the high-frequency Boundary Element Method and Surface-Based Geometrical Acoustics. https://doi.org/10.3397/in_2022_1005

The audible frequency range covers many octaves in which the wavelength changes from being large with respect to dominant features of a space to being comparatively much smaller. This makes numerical prediction of a space's acoustic response, e.g. fo... Read More about A comparison between the high-frequency Boundary Element Method and Surface-Based Geometrical Acoustics.

Analysis and control of acoustic modes in cylindrical cavities with application to Direct Field Acoustic Noise (DFAN) testing (2022)
Presentation / Conference
Hargreaves, J. (2022, August). Analysis and control of acoustic modes in cylindrical cavities with application to Direct Field Acoustic Noise (DFAN) testing. Presented at Internoise 2022, Glasgow, Scotland

It is well known that acoustic cavities have frequencies at which certain free-response ‘modes’ of propagation respond especially strongly. In the absence of significant damping, these cause peaks of high SPL in the frequency response as well as spat... Read More about Analysis and control of acoustic modes in cylindrical cavities with application to Direct Field Acoustic Noise (DFAN) testing.

A Boundary Element Method (BEM) Solver for Low Frequency Room Modes (2022)
Presentation / Conference
Cicero, A., & Hargreaves, J. A. (2022, August). A Boundary Element Method (BEM) Solver for Low Frequency Room Modes. Presented at Internoise 2022, Glasgow, Scotland

Room modes are known to be problematic in small critical listening environments. They degrade the acoustic quality at low frequencies, producing peaks and nulls in the frequency domain and ringing in the time domain. The Finite Element Method (FEM) i... Read More about A Boundary Element Method (BEM) Solver for Low Frequency Room Modes.

Raytracing in Galerkin Boundary Integral form (2022)
Presentation / Conference
Emthyas, A., & Hargreaves, J. (2022, August). Raytracing in Galerkin Boundary Integral form. Presented at Internoise 2022, Glasgow, Scotland

Raytracing is an established method for computing the late-time part of room impulse responses. But it has the drawback that only very crude Monte Carlo models of boundary scattering and diffraction are possible to include without losing its attracti... Read More about Raytracing in Galerkin Boundary Integral form.

Investigation into the effects of the geometry in cone driven midrange horns & phase plugs (2020)
Journal Article
Macdonald, L., & Hargreaves, J. (2020). Investigation into the effects of the geometry in cone driven midrange horns & phase plugs. Proceedings of the Institute of Acoustics, 42(3), https://doi.org/10.25144/13367

Midrange horn loudspeakers are usually used in professional audio applications to improve efficiency and control directivity. Because traditional lumped parameter circuits do not model phase plugs or complexities of horn geometry after the expansion,... Read More about Investigation into the effects of the geometry in cone driven midrange horns & phase plugs.

A framework for auralization of boundary element method simulations including source and receiver directivity (2019)
Journal Article
Hargreaves, J., Rendell, L., & Lam, Y. (2019). A framework for auralization of boundary element method simulations including source and receiver directivity. ˜The œJournal of the Acoustical Society of America (Online), 145(4), 2625-2637. https://doi.org/10.1121/1.5096171

The Boundary Element Method (BEM) is a proven numerical prediction tool for computation of room acoustic transfer functions, as are required for auralization of a virtual space. In this paper it is validated against case studies drawn from the ‘Groun... Read More about A framework for auralization of boundary element method simulations including source and receiver directivity.

The wave-matching boundary integral equation - an energy approach to Galerkin BEM for acoustic wave propagation problems (2018)
Journal Article
Hargreaves, J., & Lam, Y. (2019). The wave-matching boundary integral equation - an energy approach to Galerkin BEM for acoustic wave propagation problems. Wave Motion, 87, 4-36. https://doi.org/10.1016/j.wavemoti.2018.07.003

In this paper, a new Boundary Integral Equation (BIE) is proposed for solution of the scalar Helmholtz equation. Applications include acoustic scattering problems, as occur in room acoustics and outdoor and underwater sound propagation. It draws toge... Read More about The wave-matching boundary integral equation - an energy approach to Galerkin BEM for acoustic wave propagation problems.

Workshop on numerical acoustic simulation and auralisation as built environment design consultation tools (2015)
Journal Article
Hargreaves, J., & Lam, Y. (2015). Workshop on numerical acoustic simulation and auralisation as built environment design consultation tools. Acoustics bulletin / Institute of Acoustics, Nov 15,

Extended version of an article appearing in the November 2015 issue of Acoustics Bulletin, the UK Institute of Acoustics magazine. Describes an EPSRC-funded workshop, which was co-hosted by Arup and the University of Salford. For more informatio... Read More about Workshop on numerical acoustic simulation and auralisation as built environment design consultation tools.

An energy interpretation of the Kirchhoff-Helmholtz boundary integral equation and its application to Sound Field synthesis (2014)
Journal Article
Hargreaves, J., & Lam, Y. (2014). An energy interpretation of the Kirchhoff-Helmholtz boundary integral equation and its application to Sound Field synthesis. Acta acustica united with Acustica, 100(5), 912-920. https://doi.org/10.3813/AAA.918770

Most spatial audio reproduction systems have the constraint that all loudspeakers must be equidistant from the listener, a property which is difficult to achieve in real rooms. In traditional Ambisonics this arises because the spherical harmonic func... Read More about An energy interpretation of the Kirchhoff-Helmholtz boundary integral equation and its application to Sound Field synthesis.

Simulating acoustic scattering from atmospheric temperature fluctuations using a k-space method (2014)
Journal Article
Hargreaves, J., Kendrick, P., & von Hünerbein, S. (2014). Simulating acoustic scattering from atmospheric temperature fluctuations using a k-space method. ˜The œJournal of the Acoustical Society of America (Online), 135(1), 82-92. https://doi.org/10.1121/1.4835955

This paper describes a numerical method for simulating far-field scattering from small regions of inhomogeneous temperature fluctuations. Such scattering is of interest since it is the mechanism by which acoustic wind velocity profiling devices (Dopp... Read More about Simulating acoustic scattering from atmospheric temperature fluctuations using a k-space method.

Towards a full-bandwidth numerical acoustic model (2013)
Presentation / Conference
Hargreaves, J., & Lam, Y. (2013, June). Towards a full-bandwidth numerical acoustic model. Presented at 21st International Congress on Acoustics, 165th Meeting of the Acoustical Society of America, Montreal

Prediction models are at the heart of modern acoustic engineering and are used in a diverse range of applications from refining the acoustic design of classrooms and concert halls to predicting how noise exposure varies through an urban environment.... Read More about Towards a full-bandwidth numerical acoustic model.

Subjective preference of modal control methods in listening rooms (2012)
Journal Article
Fazenda, B., Wankling, M., Hargreaves, J., Elmer, L., & Hirst, J. (2012). Subjective preference of modal control methods in listening rooms. Journal of the Audio Engineering Society, 60(5), 338-349

Methods to control the unwanted effects of low-frequency modes in critical listening rooms range from complex signal processing to the positioning of loudspeakers and listeners. A rigorous scientific experiment has been conducted to evaluate the perc... Read More about Subjective preference of modal control methods in listening rooms.

Low frequency sound propagation in activated carbon (2012)
Journal Article
Bechwati, F., Avis, M., Bull, D., Cox, T., Hargreaves, J., Moser, D., …Venegas, R. (2012). Low frequency sound propagation in activated carbon. https://doi.org/10.1121/1.4725761

Activated carbon can adsorb and desorb gas molecules onto and off its surface. Research has examined whether this sorption affects low frequency sound waves, with pressures typical of audible sound, interacting with granular activated carbon. Imped... Read More about Low frequency sound propagation in activated carbon.

Simulating transient scattering from obstacles with frequency-dependent surface impedance (2011)
Presentation / Conference
Hargreaves, J. (2011, June). Simulating transient scattering from obstacles with frequency-dependent surface impedance. Presented at Forum Acusticum, Aalborg, Denmark

This paper presents an algorithm which couples the time domain Boundary Element Method (BEM) with a digital filter surface model. This aims to achieve the same extent of applicability and accuracy for transient sounds as is available for time-harmon... Read More about Simulating transient scattering from obstacles with frequency-dependent surface impedance.

Coupling of a time domain boundary element method to compliant surface models (2010)
Presentation / Conference
Hargreaves, J., & Cox, T. (2010, September). Coupling of a time domain boundary element method to compliant surface models. Presented at EAA Euroregio Conference, Ljubljana

The Boundary Element Method (BEM) can be used to predict the scattering of sound in rooms. It reduces the problem of modelling the volume of air to one involving only the surfaces; hence the number of unknowns scales more favourably with problem size... Read More about Coupling of a time domain boundary element method to compliant surface models.

A transient boundary element method for acoustic scattering from mixed regular and thin rigid bodies (2009)
Journal Article
Hargreaves, J., & Cox, T. (2009). A transient boundary element method for acoustic scattering from mixed regular and thin rigid bodies. Acta acustica united with Acustica, 95(4), 678-689. https://doi.org/10.3813/AAA.918196

Boundary Element Methods (BEMs) may be used to predict the scattering of sound by obstacles, which has accelerated the prototyping of new room acoustic treatments such as diffusers. Unlike the more popular frequency domain method, the time domain BE... Read More about A transient boundary element method for acoustic scattering from mixed regular and thin rigid bodies.

A transient boundary element method model of Schroeder diffuser scattering using well mouth impedance (2008)
Journal Article
Hargreaves, J., & Cox, T. (2008). A transient boundary element method model of Schroeder diffuser scattering using well mouth impedance. ˜The œJournal of the Acoustical Society of America (Online), 124(5), 2942-2951. https://doi.org/10.1121/1.2982420

Room acoustic diffusers can be used to treat critical listening environments to improve sound quality. One popular class is Schroeder diffusers, which comprise wells of varying depth separated by thin fins. This paper concerns a new approach to ena... Read More about A transient boundary element method model of Schroeder diffuser scattering using well mouth impedance.

A time domain boundary element method for compliant surfaces (2008)
Presentation / Conference
Hargreaves, J., & Cox, T. (2008, January). A time domain boundary element method for compliant surfaces. Presented at EURONOISE, the 155th ASA Meeting, and the 9th Congrès Français d'Acoustique, Paris, France

The best way of representing compliant surfaces in time domain prediction models, such as the transient Boundary Element Method (BEM), is currently unresolved. This is not true of frequency-domain, time-invariant models, where the common practice is... Read More about A time domain boundary element method for compliant surfaces.