The design and evaluation of an economically constructed anechoic chamber

This paper reports on a study of the design of an economic anechoic chamber so that a controlled environment would be readily available for acoustic experiments such as 3-D audio playback through a spherical loudspeaker array. It describes measurements performed to evaluate the room's acoustical performance against ISO 3745 and some ITU-R BS.1116-1 recommendations. Two custom omni-directional sound sources were developed for the mid and high frequency range to perform some of these measurements. The data from these measurements indicate that the room has a noise rating of NR15; the carpeted floor absorbs at least 50% of incident sound energy above 400 Hz, and the room exhibits free-field conditions in all directions tested up to 2 m from the centre of the room between 400 Hz and 20 kHz. Hence, this paper presents a model of how an economic anechoic chamber could be designed for high-resolution spatial audio applications (such as audio reproduction using high order ambisonics), and how such a room's acoustic performance can be assessed.