## 1 Introduction  
It has been proved that sound levels, sound pressure, or even sound power, although properly weighted, are not able to assess the annoyance that a sound may generate [1]. This is true especially for high sound pressure levels due both to the great difference between the A-weighting filter and the equal loudness contour curve at these levels [2] and to the necessity of using parameters that account for the time structure and the spectral variation of the signals, such as the psychoacoustics parameters. Unfortunately, almost all legislation still refers to overall A-weighted levels (\(L_{\text{Aeq}}\), \(L_{\text{WA}}\), \(L_{\text{PA}}\)) aimed at checking the compliance of the products. For earthmoving machines, the Directive 2000/14/EC [3] imposes limitations on the A-weighted sound power levels emitted by the machine while the Directive 2006/42/EC [4] requires information on the airborne noise emissions, in terms of A-weighted sound pressure level at the workstation, C-weighted peak instantaneous sound pressure value at the workstation, and A-weighted sound power level emitted by the machine. As the reduction of the noise levels is not strictly linked to the reduction of the annoyance, manufacturers are facing the problem of customers' complaints concerning the noise quality of the machines with increasing frequency. In the last ten years, great efforts have been made by the authors to better understand the relationship between the multidimensional characteristics of the noise signals at the operator station of compact loaders in different working conditions and the relevant auditory perception of annoyance [5]. Compact loaders, indeed, are critical as far as noise emission is concerned because the operator station is located just above the engine compartment, which cannot be completely insulated from the outside due to overheating problems. As a consequence, noise and vibration levels at the operator station are extremely high, causing uncomfortable conditions for workers. Moreover, compact loaders are widely used in dwelling areas for the activities of building construction and renovation, and the study of the quality of their noise emissions may be valuable to reduce their environmental noise impact. Results of these studies showed that loudness and sharpness are the parameters primarily related to the annoyance perception of these noise signals [6; 7]. In particular, \(S_{5}\) (fifth sharpness percentile) and \(N_{50}\) (fiftieth loudness percentile) were found to be closely related to the annoyance perception when the machines were operating in dynamic conditions. As to the different perception occurring with sounds having different loudness and/or sharpness values, subjective listening tests indicated that the minimum differences which are subjectively perceived (just noticeable differences, JND) for the loudness and sharpness of these machines are 0.8 some and 0.04 acum, respectively. Results highlighted also that the loudness JND becomes greater as the overall sound pressure level of the signal increases, while the sharpness JND has very small variations related to the overall level [8]. All of these studies followed the \"product sound quality\" approach that, although very powerful in relating the physical characteristics of the noise to the auditory perception of annoyance, requires repeated sessions of jury listening tests, which are time-consuming [9; 10; 11; 12]. In this respect, an annoyance prediction model could be extremely valuable to assess the annoyance sensation perceived by operators of earthmoving machines at their workplaces without repeating the full sound quality assessment but using prior knowledge of these machines. This approach has already been applied to many other products [13; 14; 15; 16] as well as to construction machines and some of their components [17]. The authors developed an annoyance prediction model able to evaluate the grade of annoyance at the workplace of compact loaders using objective parameters only [18].