Speaker: Dr Jonathan Hargreaves
Wed 7th Feb 2024 12:00 – 13:00 UK time. This seminar will be an hybrid event: in Maxwell 907 on campus with online access via this Teams link.
Abstract
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 on-axis a few centimetres in front of the diaphragm. Standard methods involve measuring level and/or phase at two or more points, and then fitting a monopole model to it. This works satisfactorily if the loudspeaker is omnidirectional, but it is not appropriate for ones that are not – modern cardioid subwoofers for example. This paper therefore explores an alternative definition based on a spherical harmonic representation of its directivity. This is still valid for omnidirectional sources but supports directional ones too. Its properties are investigated through simulation and used to optimise cardioid radiation from a loudspeaker.
Biography:
Jonathan Hargreaves MIOA was awarded an MEng in Engineering & Computing Science from the University of Oxford in 2000 and a PhD in Acoustic Engineering from the University of Salford in 2007, where he remains as a Lecturer in Acoustic and Audio Engineering. He is best known for his research on novel computational acoustic algorithms – notably Boundary Integral Methods – but he also has strong research interests in loudspeaker design and characterisation, material characterisation, and microphone arrays. He is a member of the IOA Research Coordination Committee and the UK Acoustics Network Special Interest Group for Computational Acoustics, and, since 2020, has had the pleasure on consulting for RAL Space on their Direct field Acoustic Testing requirements. Jonathan has had the pleasure of being involved in a wide variety of public engagement activities, including several TV appearances, and is passionate about performing, engineering and enjoying live music. He was awarded the UK Institute of Acoustics’ Tyndall Medal, for outstanding contribution to acoustics research and education, in September 2016.
Paper
This talk it an extended version of a presentation given at the IOA’s Reproduced Sound conference in November 2023. The paper that accompanied that talk can be found here.
A conference