The effects of distortion on the perception of loudness in live sound

Abstract

Distortion is a central concern in audio production, and occurs in many parts of a live sound reinforcement system. Perceived loudness is a key principal in psychoacoustics, and may be strongly affected by factors such as spatial variance and the distinct effects of nonlinearity in the signal chain. The aim of this study is to highlight the relationship between perceived loudness, and different analytical forms of distortion which relate to how loudspeaker systems might behave. Some key factors of loudness perception and basic principles of distortion are discussed. A series of listening tests confirm that there is a relationship between loudness perception and distortion, and that this effect may vary between listeners. The results are analysed using perceptually motivated metrics such as Rnonlin and Loudness Units Full Scale. Overall, the importance of controlled compression techniques and limiting to avoid clipping are reinforced, as clipping may decrease aggregate perceived loudness and increase inter-listener variance in the live events domain.