AES Munich 2009
Saturday, May 9, 09:00 — 11:00
Paper Session P17
P17 - Room Acoustics & Loudspeaker Interaction
Chair: Eddy B. Brixen
P17-1 Effects of Loudspeaker Directivity on Perceived Sound Quality—A Review of Existing Studies—William Evans, University of Surrey - Guildford, Surrey, UK; Jakob Dyreby, Søren Bech, Bang & Olufsen A/S - Struer, Denmark; Slawomir Zielinski, Francis Rumsey, University of Surrey - Guildford, Surrey, UK
The directivity of a loudspeaker system is often regarded as a prominent factor in the overall subjective quality of the reproduced sound experience. Much literature is available on the topic, and currently a broad field of opinion exists among designers. This paper provides an overview of the available literature, as well as an extended investigation into listener-based research. Results indicate that for such a widely debated topic, conclusive measurement data with regard to human listeners is limited, and, therefore, a proposal for more informative listening tests is presented.
Convention Paper 7745 (Purchase now)
P17-2 Subjective Validity of Figures of Merit for Room Aspect Ratio Design—Matthew Wankling, Bruno Fazenda, University of Huddersfield - Huddersfield, West Yorkshire, UK
Attempts have long been made to classify a room’s low frequency audio reproduction capability with regard to its aspect ratio. Common metrics used have relied on the homogeneous distribution of modal frequencies and from these a number of “optimal” aspect ratios have emerged. However, most of these metrics ignore the source and receiver coupling to the mode shapes—only a few account for this in the derivation of a figure of merit. The subjective validity of these attempts is tested and discussed. Examples are given of supposedly good room ratios with bad performance and vice versa. Subjective assessment of various room scenarios is undertaken and a ranking order has been obtained to correlate with a proposed figure of merit.
Convention Paper 7746 (Purchase now)
P17-3 A Study of Low-Frequency Near- and Far-Field Loudspeaker Behavior—John Vanderkooy, University of Waterloo - Waterloo, Ontario, Canada, B&W Group Ltd., Steyning, West Sussex, UK; Martial Rousseau, B&W Group Ltd. - Steyning, West Sussex, UK
Low-frequency loudspeaker measurements are difficult. Room reflections, mediocre anechoic chambers, and random noise play havoc with the quest. Diffraction is different in nearfield and farfield. This paper covers a range of topics that bear on these problems, such as boundary element diffraction simulations, an approximate theory for low frequencies, methods to shorten the impulse response, and nearfield characteristics. A few points are illustrated with measurements. An earlier simplified diffraction theory of Kessel is checked for axisymmetric cylindrical and rectangular boxes by boundary-element simulations, in an attempt to pin down the diffractive 4pi to 2pi transition. It turns out to have a strong connection to the acoustic center of a loudspeaker. Some measurements are made under various conditions. Shortening methods are used to minimize the deleterious effect of truncating room reflections from the impulse response.
Convention Paper 7747 (Purchase now)
P17-4 Subwoofers in Symmetrical and Asymmetrical Rooms—Juha Backman, Nokia Corporation - Espoo, Finland
A theoretical study of behavior of single and multiple subwoofers, taking also geometrical and acoustical asymmetry of practical listening environments into account, is presented. The results indicate that configurations aimed at precise cancellation of individual modes have a high sensitivity to deviations from the ideal. However, with multiple subwoofers it is possible to find robust placements that both reduce the spatial variation of the sound field and the frequency variation of the response. This, however, requires loudspeaker placements where also the height of the source from the floor is varied.
Convention Paper 7748 (Purchase now)