The Kurtosis Adjustment Models

So far, two kurtosis adjustment models have been proposed as follows:

This model was used in Zhao et al. (4) and Xie et al. (9). The adjustment formula is listed below:

This form was chosen for calculating the kurtosis-adjusted cumulative noise exposure (CNE) because Gaussian noise has a kurtosis of β=3, and the term [(ln(β)+1.9)/log(2)] is close to 10. Thus, for Gaussian noise, the kurtosis-adjusted CNE equals the unadjusted CNE. According to Equation (1), for a fixed L_Aeq,8h, the kurtosis adjusted CNE of the non-Gaussian noise (β>3) is larger than that of the Gaussian noise (β=3), which is equivalent to prolonging the noise exposure duration.

Goley et al. (10) presented another way to use kurtosis in NIHL evaluation. Goley and colleagues proposed a scheme that uses kurtosis to adjust the A-weighted equivalent sound pressure level (L_Aeq) directly. The basic form of the kurtosis-adjusted L'_Aeq was determined as follows:

whereλ is a positive constant to be determined from the dose-response correlation study, β_N is the kurtosis of the noise, and β_G=3 is the kurtosis of the Gaussian noise. Taking noise-induced permanent threshold shift as the dependent variable and L_Aeq and log(β_N/3) as independent variables, the coefficient λ was calculated by multiple linear regression model. Based on the animal (chinchilla) model, Goley obtained λ=4.02. If the model is applied to humans, the value needs to be re-estimated using human data. Using Goley’s model is equivalent to adding an increment determined by the second term of the formula to the resulting total sound pressure level.