Efficiency of loudness models for the evaluation of airplane cockpit noise comfort

Abstract

Aircraft interior noise is a major design stake with respect to airline requirements for passenger and crew comfort. The focus was put here on cockpit noise. The goal of this study was to evaluate unpleasantness of such sounds and to propose metrics for its prediction. Six sounds recorded in various airplanes were used; one of them was modified in order to reduce the level of an emerging low-frequency component, leading to a number of seven stimuli. These stimuli were used in a pair-comparison experiment in a sound-proof booth. 31 listeners participated to the experiment. Results could be analysed using a BTL model, which provided an unpleasantness scaling of the stimuli. Unpleasantness was clearly related to loudness; due to the high level in the very low frequency bands, A-weighted level failed to represent loudness. Two loudness models were also used: the ISO-532 one and the ANSI S3.4 one. It appeared that the former gave better results. It is argued that this is due to the evolution of loudness values in the low frequency range, which is different between these two models.