The role of sound emergence for aircraft noise annoyance

The metric emergence relates source-specific sound levels to background noise. The approach of subtracting a residual sound level (total sound level without the level of a specific source) from the total sound level follows the definition of emergence in ISO 1996-1. Using exposure and survey data of the German NORAH study, the impact of emergence on aircraft noise annoyance was analysed. As total background sound levels were not available, information about source-specific and combined noise levels was used instead. For participants exposed to aircraft and road traffic noise for the emergence substitute es(air/road), road traffic sound levels for daytime (LAeq,road,day) of the home address of survey participants were subtracted from the combined sound levels of aircraft and road traffic noise (LAeq,air+road,day) with road traffic noise regarded as a proxy for background noise. Similar, for participants exposed to aircraft and railway noise, LAeq,rail,day were subtracted from LAeq,air+rail,day to obtain es(air/rail). The percentage of people highly annoyed (%HAV) by aircraft was predicted by LAeq,air,day for subgroups with es(air/road) and es(air/rail) ≥ 3 dB and es(air/road) / es(air/rail) < 3 dB. Results: Particularly in low aircraft noise-exposed areas, %HAV is higher for those with higher values of es(air/road) and es(air/rail), respectively.