Acoustic Optimisation at Workplaces Based on Sound Quality: The Case of Time-Varying Noise Signals

This paper describes the use of a multi-objective optimisation code aimed at identifying solutions which improve the sound quality at the operator station of earth moving machinery during real working conditions. A previous study considered the case of stationary noise signals and a multi-objective genetic algorithm was used to find the modifications in the input spectrum which led to the minimisation of the time-Averaged values of loudness and sharpness. This paper presents a different optimisation approach aimed at adapting the previous one to the case of time-variant noise signals, typical of real working conditions. New input variables to describe the time variant characteristics of the system were identified and a numerical module for the correct calculation of loudness for time-variant sounds was developed according to the DIN-45631/A1 procedure. Finally the multi-objective genetic algorithm was used to find the modifications in the input system which lead to minimise the percentile values of loudness and sharpness parameters. This procedure was applied to different noise signals, all recorded at the operator position of loaders in working conditions. The results show a significant link between sound quality condition and spectral characteristics of the noise signals making it possible to evaluate spectral variations needed to obtain psychoacoustic improvements.