Building noise criterion curves, BNC, for interior spaces

Abstract

This paper presents an updated set of noise criterion (NC) curves that are renamed building noise criterion (BNC) curves. They are based, in part, on the latest definition of four‐band speech interference level and on “spectrum balance,” that is to say, the premise that the loudnesses of all bands containing the same number of critical bands should be equal, as calculated by Stevens Mk. VII perceived loudness method. The curves are extended downward in frequency to include the two octave bands with mean frequencies at 16 and 31.5 Hz. Finally, the high‐sound level, low‐frequency region of the curves [Blazier, Noise Control Eng. 16, 64–73 (1981)] are demarked to show where human annoyance will probably result from vibrations caused by such noise levels in contemporary building construction. The paper details the use of the BNC curves in writing a specification for building construction and in determination of the conformance of the measured result to the specification, or in rating an existing noise. Particularly important are the procedures given for determining “spectrum imbalance.” The handling of two typical types of imbalance are discussed: (1) an acceptable speech interference level accompanied by high low‐frequency band levels; (2) acceptable low‐frequency band levels accompanied by a very low speech interference level.