Single number ratings for assessing open offices

Abstract

A large number of interzone attenuation measurements have been made on a variety of arrangements of open office components. All measurements were made in one-third octave bands using a computer controlled analyzer and followed in essence the procedure described in U. S. General Services Administration document PBS C.2. Six different methods of reducing the measurements to a single number rating were correlated with articulation index used as a reference. The NIC's rating used in PBS C. 2 did not correlate with articulation index as well as simple A-weighted level differences. Office and ceiling systems are typically assessed by making measurements at a height of 4 ft above the floor simulating seated humans. This need not be adhered to when only ceiling systems are to be rated. The effect reducing this height was examined both experimentally and theoretically, and good agreement was obtained. The range in measured values can be approximately doubled by reducing the measuring height from 4 to 2 ft. Again, using articulation index as a criterion, the NC 40 procedure for rating masking noise described in the PBS documents was compared with other more commonly used methods. The four-octave-band speech interference level was found to be an improvement.