Addressing psychoacoustic uncertainty in noise codes

Noise codes commonly impose methods and requirements to promote livability and well-being. The codes typically use physical quantities like sound pressure levels. Often the levels are A-weighted to represent human frequency sensitivity, but A-weighting alone is often insufficient to characterize human response. When sound levels inadequately represent listener perception, there is psychoacoustic uncertainty, and the codes may fail to achieve their desired intent. Psychoacoustic metrics are an alternative specifically formulated to represent human perception. This paper presents examples of sound levels that underperform psychoacoustic metrics for sounds generated by ball drops and IT equipment. Reasons for metric performance are given. The benefits of psychoacoustic certainty obtained from metrics representing listener perception for acoustic design, build, and qualification are explained.