A supplement of sound measurement technique by an online quality test procedure for the indices LEQ and LX%

As is well known every measured sound index like L-eq and L-x% has limited accuracy due to the usually occurring stochastic level fluctuations. This limitation can be taken into account adequately by calculating the confidence limits from the signal's microstatistic structure. The basic theory and its preconditions close to measurement practice have been established formerly by the author. An overview is given here. The method provides to work quality controlled in a flexible way. A PC-software for online performance is now available. Tested by field measurements this technique is applicable on the quality-monitored short-term separation of level components of different sound sources in the outdoor environment. The final results are the L-eq of the source of interest, the confidence limits of the L-eq and its resolution level. Resolution limits down to 10 dB below the residual sound level are practicable. This kind of application has already been introduced and used in Germany to some extent. At the present state of the art the tool also can be applied on sound transfer measurements, especially with relatively high background level in a receiver room, and on examining the influence of a small absorption model area for in-room damping, to be extended later to full scale. (C) 2001 Academic Press.