Tonal noise in buildings: Current practice in measurement and assessment

A review of the research and guidelines for tones that may be applied towards buildings is discussed. A tone is defined as a sound where most of the energy is concentrated at a single frequency, and is more likely to be detected at low levels. Tones are rarely found in areas without considerable background noise or masking, which was further found to be dependant on both the level of the tone over the background noise, and the level of the background noise itself. Kryter and Pearsons developed a methodology based on the judgment of random train noise containing a pure tone, resulting in the Tone Corrected Perceived Noise Level. The Federal Aviation Regulation (FAR) 36, Section A36.4 outlines the process known as the Effective Perceived Noise Level (EPNL), which is a single number evaluator of the subjective effects of noise. An indoor setting also is dependent on many non-acoustical factors, including room aesthetics and occupant occupation.