Sound Absorption at Low Frequencies: Room Contents as Obstacles

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 preliminary study of the influence of furniture on low frequency room response was performed by introducing a “reference obstacle” at three positions within an enclosure which previously had been numerically modelled. 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 large solid 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. Obstacles placed along a wall or in room corners will produce a greater change in room response, when compared with a central location.