PRACTICAL ASPECTS OF MLS MEASUREMENTS IN BUILDING ACOUSTICS

The maximum length sequence (MLS) technique is established in various acoustic measurements for fast and accurate broadband determination of acoustic quantities, In this paper a general overview of the benefits and limitations of the MLS technique in building acoustics is present ed. Furthermore, an approach is described to investigate the influence of time variances on the use of synchronous averaging. It is shown th at averaging with the presence of time variances causes an apparent le vel loss, Time variances are investigated specifically in the context of temperature drift in a room and of wind fluctuations under free fie ld conditions, For both cases formulae are derived to enable error est imation for practical cases. The theory is validated by experimental r esults. (C) 1997 Elsevier Science Ltd.