Effects of speaker location and orientation on room sound fields and room to room noise reduction

Abstract

ASTM E336 requires that loudspeakers be placed at least 5 m from a partition under test, and if that is not possible, then in the corners opposite the partition. The standard further advises that if directional loudspeakers are used in the corners, they should be faced into the corners. In practice, speakers are usually placed in the corners of residential and smaller office spaces, but not in the corners of large spaces. Recent experience has uncovered two effects that need further study. First, when loudspeakers are faced into the corners of a large room, the sound spectrum is strongly colored with a large dip typically in the 100 to 500 Hz range. This effect can be seen in smaller rooms, but is much less pronounced there so it is not normally noticed. Second, the noise reduction measured for a partition of a large room appears to vary depending on whether the speakers are in the corners or not, with lower noise reduction when the speakers are in the corners. This effect does not appear to depend on whether the speakers are faced into the corners or not. Data and any further observations and conclusions developed will be presented.