Dr Jonathan Hargreaves' Outputs (49)

Understanding human responses to air source heat pump noise: examining tonal changes and operating cycles (2024)
Presentation / Conference Contribution

Air Source Heat Pumps are pivotal in the Government of the United Kingdom's target of achieving net zero carbon emissions by 2050. However, their widespread adoption faces challenges, with noise being among the main barriers to entry and a restrictin... Read More about Understanding human responses to air source heat pump noise: examining tonal changes and operating cycles.

Higher-fidelity analysis of air source heat pump noise via scanning intensity measurement (2024)
Presentation / Conference Contribution

The need to shift to reduce carbon emissions to hit Net Zero is currently driving plans for large scale rollouts of Air Source Heat Pumps (ASHPs), due to their increased thermal efficiency and lack of direct carbon emissions. Concern exists, however,... Read More about Higher-fidelity analysis of air source heat pump noise via scanning intensity measurement.

Confidence limits for coherence – toward a better understanding of its use as a diffuse field metric for quantifying the quality of Direct Field Acoustic Noise (DFAN) Testing systems (2024)
Presentation / Conference Contribution

To determine the degree of diffuseness of a particular acoustic field, an oft-considered metric is the coherence between spaced pairs of measurement microphones. This is useful because the expected theoretical ‘sinc2’ trend for a diffuse field is wel... Read More about Confidence limits for coherence – toward a better understanding of its use as a diffuse field metric for quantifying the quality of Direct Field Acoustic Noise (DFAN) Testing systems.

Extending the Low Frequency Acoustic Centre Concept to Directional Loudspeakers (2023)
Presentation / Conference Contribution

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.

Adventures in High Intensity Acoustic Testing: a Loudspeaker System for Small-Scale Tests (2023)
Presentation / Conference Contribution

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.

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

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.

A 'Surface-based' Geometrical Acoustic formulation within a Galerkin Boundary Element framework (2022)
Thesis
Emthyas, A. A 'Surface-based' Geometrical Acoustic formulation within a Galerkin Boundary Element framework. (Dissertation). University of Salford

As sound propagates within a room, it experiences high-order reflection, diffraction, and scattering. This causes the reflection density to increase over time, such that the sound field becomes diffuse and chaotic. Under these conditions, there is li... Read More about A 'Surface-based' Geometrical Acoustic formulation within a Galerkin Boundary Element framework.

Metric-based optimisation of acoustic lenses and waveguides (2022)
Thesis

This dissertation develops an automated procedure for the design of acoustic waveguides that can support single parameter (1P) wave propagation over a large bandwidth. 1P waves include plane, cylindrical and spherical waves, and the waveguides aim to... Read More about Metric-based optimisation of acoustic lenses and waveguides.

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.

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.

A time method version of the transfer matrix method (2021)
Presentation / Conference Contribution

Porous absorbers are ubiquitous in acoustics applications. They are, for example, widely used to
control reverberation in rooms and cavities, or to provide attenuation in ducts. Because of this, they
have attracted significant research effort to be... Read More about A time method version of the transfer matrix method.

A tutorial on the finite and boundary element methods in acoustics (2021)
Presentation / Conference Contribution

The Finite Element Method (FEM) and Boundary Element Method (BEM) are established numerical simulation techniques that are widely used in Engineering, including in Acoustics. This tutorial lecture will give a brief tour of both methods, some discussi... Read More about A tutorial on the finite and boundary element methods in acoustics.

Investigation into the effects of the geometry in cone driven midrange horns & phase plugs (2020)
Presentation / Conference Contribution

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.

Graduate programs in acoustics at the University of Salford, United Kingdom (2020)
Presentation / Conference Contribution

Salford is one of the UK's leading centers for research and teaching in acoustics and audio. The courses are delivered by a research-active academic team at the very pinnacle of the profession, with an attractive staff to student ratio. Our taught co... Read More about Graduate programs in acoustics at the University of Salford, United Kingdom.

Modelling the perception of percussive low frequency instruments in rooms (2020)
Thesis
Howard, M. Modelling the perception of percussive low frequency instruments in rooms. (Dissertation). University of Salford

Throughout the study of room acoustics, adverse effects and methods of controlling
and mitigating modal behaviour are a well researched topic. However, despite this, a
gap between objective metrics and subjective results is still prevalent, thus re... Read More about Modelling the perception of percussive low frequency instruments in rooms.

A framework for auralization of boundary element method simulations including source and receiver directivity (2019)
Journal Article

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.

A transformation approach for efficient evaluation of oscillatory surface integrals arising in three-dimensional boundary element methods (2016)
Journal Article

We propose a method for efficient evaluation of surface integrals arising in boundary element
methods for three-dimensional Helmholtz problems (with real positive wavenumber k), modelling
wave scattering and/or radiation in homogeneous media. To re... Read More about A transformation approach for efficient evaluation of oscillatory surface integrals arising in three-dimensional boundary element methods.