Keith Attenborough | The Open University (original) (raw)

Uploads

Papers by Keith Attenborough

The Journal of the Acoustical Society of America

The Reflections series takes a look back on historical articles from The Journal of the Acoustica... more The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

Academia Engineering, Aug 24, 2023

Journal of the Acoustical Society of America, May 1, 2022

PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO. eBooks, Dec 1, 2004

Springer eBooks, 2007

... The pressure at the receiver is the sum of four terms that correspond to the sound paths SgER... more ... The pressure at the receiver is the sum of four terms that correspond to the sound paths SgERg, Si ERg, SgERi, and SiERi. ... For example, the diffracted wave along the path SgERg would be given by P1 = Att1ei[k(r0+rr )+π/4] (20) ...

HAL (Le Centre pour la Communication Scientifique Directe), 2008

Journal of the Acoustical Society of America, 2008

In a study of hooded crow communication over open fields an excellent correspondence is found bet... more In a study of hooded crow communication over open fields an excellent correspondence is found between the attenuation spectra predicted by a “turbulence-modified ground effect plus atmospheric absorption” model, and crow call attenuation data. Sound propagation predictions and background noise measurements are used to predict an optimal frequency range for communication (“sound communication window”) from an average of crow call spectra predicted for every possible combination of the sender/receiver separations 300, 600, 900, and 1200m and heights 3,6,9m thereby creating a matrix assumed relevant to crow interterritorial communication. These predictions indicate an optimal frequency range for sound communication between 500Hz and 2kHz. Since this corresponds to the frequency range in which crow calls have their main energy and crow hearing in noise is particularly sensitive, it suggests a specific adaptation to the ground effect. Sound propagation predictions, together with background noise measurements and hearing data, are used to estimate the radius of the hooded crow active space. This is found to be roughly 1km in moderately windy conditions. It is concluded that the propagation modeling of the sort introduced here could be used for assessing the impact of human noise on animal communication.

Designs with uniformly distributed slits normal or inclined to the incident surface exhibit a gre... more Designs with uniformly distributed slits normal or inclined to the incident surface exhibit a great potential because of their simplicity and good acoustical performance. However, production of materials of this sort is challenging as the required fabrication precision is very high. This paper deals with additive manufacturing, modeling, and impedance tube testing of a few slitted geometries and their variations, including cases where the dividing walls between slits are perforated. They were designed to be producible with current 3D printing technology and provide reliable measurements using standardized equipment. The normal incidence sound absorption curves predicted analytically and numerically were verified experimentally. It is observed that such simple configurations may lead to absorption properties comparable to porous acoustic treatments with more complex microstructure. The good agreement between the predictions and measurements supports the validity of the multi-scale modeling employed

한국소음진동공학회 국제학술발표논문집, Aug 1, 2003

Journal of Sound and Vibration, Jul 1, 1989

Springer eBooks, 1985

Studies of outdoor sound propagation, particularly at near grazing-incidence and of the phenomeno... more Studies of outdoor sound propagation, particularly at near grazing-incidence and of the phenomenon of acoustic-to-seismic coupling have motivated a search for suitable models for the acoustical characteristics of outdoor ground surfaces. In many instances of outdoor propagation, it has been found possible to obtain sufficient accuracy by assuming both that the ground is locally-reacting, so that it may be described by its normal surface impedance (Zs), and, by calculating Zs from empirical power law relationships for the characteristic impedance of fibrous absorbents1. These relationships introduce a single parameter, the flow resistivity of the surface. The range of validity of these empirical relationships was stated by their authors to be 0.01 < (fΩo/Rs) < 1; where f is the frequency in Hz, Ωo is the equilibrium density or air in Kg m -3 and Rs is the flow resistivity in N s m-4. Moreover the relationships were derived from data for dry fibrous materials with porosities near unity and flow resistivities ranging from 5000 to 80000 N s m-3. Despite this, the relationships have been used successfully in combination with well-established theory for propagation from a point source above an impedance boundary to describe excess attenuation, up to 1000 Hz, over short ranges encompassing a wide variety of ground surfaces outdoors 2. The single parameter that, consequently, describes the acoustical behaviour of the ground has been called the effective flow resistivity (Rse).

Journal of Soil Science, 1992

SUMMARYTwo acoustic techniques for determining the air‐filled porosity and air permeability of so... more SUMMARYTwo acoustic techniques for determining the air‐filled porosity and air permeability of soil surfaces, and the near‐surface variation of these properties with depth, have been applied to several soils in situ. The techniques depend upon an inversion process using data on sound propagation near to the soil surface and through the soil surface. The measured difference in acoustic spectra received by two vertically separated microphones above the ground surface and by probe microphones beneath the surface were matched theoretically to deduce the porosity of air‐filled connected pores and an effective air permeability which depends on pore shape and size distribution. This modified permeability parameter and the acoustically deduced porosity varied realistically with surface sealing and compaction. The acoustically deduced porosities were within 10% of those obtained conventionally. Changes in acoustically deduced parameters occurred with changes in moisture content both in soil ...