Sound Absorption at Low Frequencies: Room Contents as Absorbers

Abstract

A description is given of sound absorption in small-furnished rooms at low frequencies. The objective of the work was to characterise room absorption due to contents such as furniture and to develop a model of absorption appropriate for a modal description of contained sound fields at low frequencies. In this paper, a study of the influence of furniture on low frequency room response was performed by introducing idealised contents into an enclosure which previously had been numerically modelled. The contents were solid objects with absorbent coverings and wholly absorbing objects. A real item of furniture also was measured and modelled for inclusion in the room model. Eigenfrequency shifts and selective modal damping were observed throughout the frequency range of interest, 20-200 Hz, and the numerical model was able to take these effects into account, showing overall good agreement with measurements. It is shown that when a solid or absorbing item is introduced into a room there is little effect on the room frequency response for frequencies below 50 Hz. Between 50 Hz and 200 Hz the effect is more pronounced and the influence of location becomes apparent. Contents placed along a wall or in room corners will produce a greater change in room response, when compared with a central location.

Analysis and optimization of the chamfered pyramid and evaluation of geometrical parameters’ effect on its sound absorption coefficient

“…The sound absorbers of the anechoic chamber could be flat, 4 wedge, 5 conical, 6 or pyramidshaped. 1 Wave method, 7 numerical methods (like the finite element method 6,7 and finite difference time-domain method 8 ) and experimental methods (including measuring the sound absorption coefficient of perpendicular impact in the impedance tube [9][10][11][12] and the actual sound absorption coefficient in the reverberation room 1 ) can be used to determine the absorption coefficient of sound absorbers. To enhance the effectiveness of pyramid sound absorbers at absorbing sound, a novel design for this type of absorber is proposed in this paper.…”

Sound Absorption at Low Frequencies: Room Contents as Obstacles

“…The microphone positions were unaltered to allow comparisons between results for the empty room and room with the reference obstacle. These comparisons served as a basis for the quantification of the effect on room response of real furniture to be described in a future paper [14].…”