Influenza di condizioni operative e caratteristiche progettuali sulla sound quality di pale caricatrici compatte

Nowadays, the improvement of the noise climate at the operator station of construction machines is a key issue. In fact, the 2003/10/EC Directive on health and safety requirements for noise exposure at work has currently being transposed in all the European Member States, introducing lower noise limits. On the other hand, the market requests are more and more oriented to machines with high-level performances and this trend is making noise one of the key factors for facing the strong competition. In this context, a research project is in progress aiming at characterising the noise climate at the operator station of skid steer loaders during actual working conditions. This paper, in particular, presents some results of a series of binaural measurements carried out at the operator station of three compact loaders, different for dimension and power, with two main goals. Firstly, to investigate in more detail the suitability of the different physical and psycho-acoustic parameters in specifying the "character" of these kinds of noise signals. Then to identify which parameters describe at best the auditory perception of these signals with respect to some desired conditions of comfort. Subjective listening tests performed on these three different compact loaders handling gravel and loam showed that sharpness and loudness are the parameters which correlate best to the subjective perception of annoyance. In addition, the use of a proper metric based on the spectral and temporal analysis of both acoustic (Fig. 4) and psychoacoustic (Fig.3) parameters permitted to deeply investigate which machine characteristics and/or working conditions are more related to the auditory perception. In fact, noise components generated by the hydraulic system and noise components associated with the machine working with gravel turned out to have the greatest impact on the annoyance judgments. This is because they influence both the medium-high frequency range affecting the sharpness values and the loudness variation over time.