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 three A-weighted sound pressure levels {30, 40, 50} dB and four 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.