Adaptive Volume Control for Sound Masking Systems: How It Works and Analysis of Performance

Basic sound masking systems were introduced in the 1970s to improve speech privacy in open plan offices. Since then, various features have been introduced to improve the efficiency and performance of sound masking systems. Amongst other things, the need to increase and decrease the masking sound level depending on the activity and noise level within the workspace was addressed. Today, most sound masking system controllers permit complex time/level programs to be stored and used for different office zones. The aim of this paper is to show how the real-time analysis of the L10% and L99% of the sound level in the open plan can be used to efficiently adapt and control the volume of the masking sound. The effect of various parameters that can used to modify the rate of sound level increase/decrease is also presented. The number of sound level sensors required per zone is discussed. Results obtained on various installations are analysed and presented, and the performance of the adaptive volume control is compared to timer-based functions.