Kurtosis-Adjusted LAeq,8h

The kurtosis adjustment was calculated according to Eq. 1 (Goley et al. 2011). Taking actual NIPTS as the dependent variable and L_Aeq,8h and log₁₀(β_N/3) as independent variables, the coefficient λ was calculated by multiple linear regression model:

where b₀ is the NIPTS-intercept; b₁ and b₂ are the regression coefficients representing the change in NIPTS relative to a one-unit change in L_Aeq.8h and log₁₀(β_N/3), respectively; ɛ is the model’s random error (residual) term. The regression analysis obtains the optimal values for b₀, b_1, and b₂ that minimizes ε, and λ = b₂/b₁. The dependent variable is actual NIPTS₃₄₆, that is, the average of actual NIPTS at 3, 4, and 6 kHz. The model was validated by comparing the difference between actual NIPTS₃₄₆ and estimated NIPTS₃₄₆ (with or without kurtosis adjustment) using the ISO 1999:2013 formula.