Listening space reduction calculations

Abstract

Listening space reduction analysis has been applied recently by several authors to evaluate the relative reduction of distance or space within which listeners can effectively detect and recognize important sound sources, due to increased acoustic masking caused by a known increase in masking noise. The approach balances the increased masking noise level by reducing source-listener distance so that propagation loss is commensurately reduced. Its recent applications have not considered all important parameters, including listener hearing sensitivity and directionality, listener cognitive signal processing gain, non-uniform acoustic propagation loss, and temporal and spatial distributions of masking noise variability. Here we derive the listening distance and space expressions from the sonar equation, accounting for the parameters above. Listening space reduction calculations are insensitive to some uncertain parameters, including source level and detection threshold (for non-human listeners) that are required for communication space calculations. The method is applicable to any sound type, including predator sounds, prey sounds, conspecific communications, and natural sounds. A modified version of the method is derived for echolocation sounds, and a corresponding echolocation space reduction factor is derived.