Aeroacoustics of the Bullroarer
Abstract:The present paper is about the physical understanding and a complete theoretical modelling of the sounding instrument called bullroarer and used by aboriginal tribesmen. The running of the bullroarer clearly involves aeromechanical aspects, closely related to the process of autorotation, as well as aeroacoustical aspects. Both are investigated here. The mechanical equations are solved in a first step, using a set of two–dimensional unsteady RANS computations as a way to deduce the instantaneous aerodynamic moment and forces. The kinematics and the unsteady forces are used in a second step to calculate the radiated sound field, according to the acoustic analogy. Preliminary theoretical results for the autorotation sound of a rectangular plate in stabilised conditions are found to agree well with measurements performed in an open-jet anechoic wind tunnel. The sound synthesis of a bullroarer based on the physical model is finally shown to fairly reproduce the main features observed in a typical time-frequency analysis.
Document Type: Research Article
Publication date: 2006-09-01
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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