Sound emergence as a predictor of short-term annoyance from wind turbine noise

While sound emergence is used in several countries to regulate wind energy development, there is no published evidence that it is a relevant noise descriptor for this purpose. In the present work, we carried out two listening tests to evaluate the merits of sound emergence. Three definitions of sound emergence were considered: the one in ISO 1996-1, sound emergence under audibility condition $e_{UAC}$, and spectral emergence $e_{SP}$. We also considered the specific to residual ratio and loudness metrics. In each listening test, the sound stimuli consisted of 48 sound stimuli at 3 A-weighted sound pressure levels $\{30, 40, 50\}$~dB and 4 specific-to-residual ratios $\{-10, -5, 0, +5 \}$~dB. The results lead to the conclusion that short term annoyance is better predicted by the total sound pressure level than by sound emergence, whatever the definition considered for the latter, or than by the specific to residual ratio. Short-term annoyance is slightly better predicted by $e_{UAC}$ than by $e$, while $e$ is a better predictor than $e_{SP}$. The total sound pressure level and the loudness metrics performed similarly. Furthermore, the results provide evidence that sound emergence is a poor predictor of the audibility of wind turbine sounds.