All Outputs (22)

Iterative metric-based waveguide optimisation (2023)
Presentation / Conference
MacDonald, L., Oclee-Brown, J., Dodd, M., & Hargreaves, J. (2023, October). Iterative metric-based waveguide optimisation. Paper presented at 155th Audio Engineering Society Convention, New York

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.

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.

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 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.

A stable time domain BEM for diffuser scattering (2007)
Presentation / Conference
Hargreaves, J., & Cox, T. (2007, September). A stable time domain BEM for diffuser scattering. Presented at 19th International Congress on Acoustics, Madrid

Boundary Element Methods (BEMs) may be used to model scattering of sound by surfaces such as diffusers, accelerating prototyping of new Room Acoustics treatments. Unlike the more widely used frequency domain method, the time domain BEM is usually sol... Read More about A stable time domain BEM for diffuser scattering.

A stable transient BEM for diffuser scattering (2005)
Presentation / Conference
Hargreaves, J., & Cox, T. (2005, October). A stable transient BEM for diffuser scattering. Presented at 150th Meeting of the Acoustical Society of America, Minneapolis

Boundary Element Methods (BEM) may be used to model scattering from hard rigid surfaces such as diffusers. They have the advantage over volumetric methods that only the surface need be meshed and the surface velocity potential found. Unlike the mor... Read More about A stable transient BEM for diffuser scattering.

Improving the bass response of Schroeder diffusers (2003)
Presentation / Conference
Hargreaves, J., & Cox, T. (2003, November). Improving the bass response of Schroeder diffusers. Presented at IOA Soundbite, Oxford

Room acoustic diffusers can be used to treat the acoustics of critical listening environments. A Schroeder diffuser is a popular type of diffuser which has the property of producing grating lobes of similar energy at most integer multiples of the des... Read More about Improving the bass response of Schroeder diffusers.

Metric based development of acoustic lenses and waveguides
Presentation / Conference
MacDonald, L., Oclee-Brown, J., & Hargreaves, J. Metric based development of acoustic lenses and waveguides. Presented at Reproduced Sound 2022, Bristol

This paper investigates and develops an automated design procedure for acoustic waveguides, to modify them to be better at supporting single parameter (1P) wave propagation. The design process is driven by two new performance metrics that are calcula... Read More about Metric based development of acoustic lenses and waveguides.

Measurement of the elastic modulus of homogeneous materials by a bending wave speed method
Presentation / Conference
Esposito, A., Hargreaves, J., Romano, R., & Cicero, A. Measurement of the elastic modulus of homogeneous materials by a bending wave speed method. Presented at Forum Acusticum, Online

Elastic modulus is one of the most important mechanical properties of homogeneous materials. It describes the dynamic behaviour of elastic and viscoelastic materials, strongly affecting both panel modes and coincidence frequencies, so is an important... Read More about Measurement of the elastic modulus of homogeneous materials by a bending wave speed method.

Non-cuboid iterative room optimizer
Presentation / Conference
Petrolli, R., D'Antonio, P., Storyk, J., Hargreaves, J., & Betcke, T. Non-cuboid iterative room optimizer. Presented at Forum Acusticum, Online

In small room acoustics, the range from the first resonant frequency up to the Schroeder frequency is dominated by modal resonances and the Speaker-Boundary Interference Response (SBIR). Both are very sensitive to the positioning of sources, receiver... Read More about Non-cuboid iterative room optimizer.

Optimising sound field synthesis using acoustic cross-energy metrics
Presentation / Conference
Hargreaves, J. Optimising sound field synthesis using acoustic cross-energy metrics. Presented at Forum Acusticum, Online

When evaluating or optimising the accuracy of sound field synthesis, it is commonplace to only consider the error in the pressure field that is reproduced. While this is justifiable perceptually - pressure is what we hear - it neglects error in parti... Read More about Optimising sound field synthesis using acoustic cross-energy metrics.

Synergies between the high-frequency Boundary Element Method and Geometric Acoustics
Presentation / Conference
Hargreaves, J. Synergies between the high-frequency Boundary Element Method and Geometric Acoustics. Presented at Forum Acusticum, Online

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 Synergies between the high-frequency Boundary Element Method and Geometric Acoustics.

Acquisition of bi-directional reflectance functions by Nearfield Acoustical Holography – a preliminary study
Presentation / Conference
Hargreaves, J. Acquisition of bi-directional reflectance functions by Nearfield Acoustical Holography – a preliminary study. Presented at International Congress on Acoustics 2019, Aachen

It is well known that material absorption and scattering is dependent on incidence and observation angle. Despite this, the corresponding standardised coefficients, which are used to represent these mechanisms within computational acoustic models, ag... Read More about Acquisition of bi-directional reflectance functions by Nearfield Acoustical Holography – a preliminary study.

Time domain modelling of room acoustics
Presentation / Conference
Lam, Y., & Hargreaves, J. Time domain modelling of room acoustics. Presented at Acoustics 2012, Nantes, France

Time domain modelling offers many advantages for room acoustics investigations. It directly generates the room’s impulse response which is an important piece of information for acoustic quality assessment. It is efficient for broadband calculations o... Read More about Time domain modelling of room acoustics.

Implementing wave field synthesis in an ITU spec listening room part 2: Bass without modes
Presentation / Conference
Hargreaves, J., & Wankling, M. Implementing wave field synthesis in an ITU spec listening room part 2: Bass without modes. Presented at Reproduced Sounds 2011, Brighton

In recent years various sound reproduction systems have been proposed which attempt to use multiple transducers to tame the modal behaviour often prominent in rooms at low frequencies. Of particular interest is the Controlled Acoustic Bass System (C... Read More about Implementing wave field synthesis in an ITU spec listening room part 2: Bass without modes.

A high-frequency BEM for 3D acoustic scattering
Presentation / Conference
Hargreaves, J., Lam, Y., Langdon, S., & Hewitt, D. A high-frequency BEM for 3D acoustic scattering. Presented at 22nd International Congress on Sound and Vibration, Florence. Italy

The Boundary Element Method (BEM) is a powerful method for simulating scattering of acoustic waves which has many advantages, particularly when the problem concerns an object in an unbounded medium. Its applications are however limited in practice be... Read More about A high-frequency BEM for 3D acoustic scattering.