Generalization of a 3-D resonator model for the simulation of spherical enclosures

A rectangular enclosure has such an even distribution of resonances that it can be accurately and efficiently modelled using a feedback delay network. Conversely, a non rectangular shape such as a sphere has a distribution of resonances that challenges the construction of an efficient model. This work proposes an extension of the already known feedback delay network structure to model the resonant properties of a sphere. A specific frequency distribution of resonances can be approximated, up to a certain frequency, by inserting an allpass filter of moderate order after each delay line of a feedback delay network. The structure used for rectangular boxes is therefore augmented with a set of allpass filters allowing parametric control over the enclosure size and the boundary properties. This work was motivated by informal listening tests which have shown that it is possible to identify a basic shape just from the distribution of its audible resonances.Comment: 39 pages, 16 figures, 6 tables. Accepted for publication in Applied Signal Processin

Proceedings of the EAA Spatial Audio Signal Processing symposium: SASP 2019

International audienc

Virtual audio reproduced in a headrest

When virtual audio reproduction is simultaneously required in many seats, such as in aircraft or cinemas, it may be convenient to use loudspeakers mounted inside each seat's headrest. In this preliminary study, the feasibility of virtual audio reproduction in the headrest of a single seat is explored using an inversion technique to compensate for crosstalk and the synthesis of head related transfer functions. Although large changes in the magnitude of the signals reproduced at the listener's ears are observed as the listener moves their head within the headrest, informal listening tests indicate that the reproduced acoustic images are surprisingly stable in about an eighth of an arc either side of the loudspeaker positions. Not surprisingly, frontal images are more difficult to reproduce with headrest loudspeakers

Multi-point nonlinear spatial distribution of effects across the soundfield

This paper outlines a method of applying non-linear processing and effects to multi-point spatial distributions of sound spectra. The technique is based on previous research by the author on non-linear spatial distributions of spectra, that is, timbre spatialisation in the frequency domain. One of the primary applications here is the further elaboration of timbre spatialisation in the frequency domain to account for distance cues incorporating loudness attenuation, reverb, and filtration. Further to this, the same approach may also give rise to more non-linear distributions of processing and effects across multi-point spatial distributions such as audio distortions and harmonic exciters, delays, and other such parallel processes used within a spatial context

Wind turbine acoustics

Available information on the physical characteristics of the noise generated by wind turbines is summarized, with example sound pressure time histories, narrow- and broadband frequency spectra, and noise radiation patterns. Reviewed are noise measurement standards, analysis technology, and a method of characterizing wind turbine noise. Prediction methods are given for both low-frequency rotational harmonics and broadband noise components. Also included are atmospheric propagation data showing the effects of distance and refraction by wind shear. Human perception thresholds, based on laboratory and field tests, are given. Building vibration analysis methods are summarized. The bibliography of this report lists technical publications on all aspects of wind turbine acoustics