Aircraft noise-monitoring according to ISO 20906. Evaluation of uncertainty derived from the classification and identification of aircraft noise events

Noise monitoring continues to be one of the most important tools in noise management around airports, since noise pollution is a serious problem for the surrounding communities. The monitoring units must be reliable and precise in order to ensure the quality of the results provided. As a previous step to achieve this, it is necessary to make an estimation of the uncertainty of the results, taking into account the contribution of every single element in the measurement chain. Among other contributions to uncertainty as listed in ISO 20906, the events marking system has an influence on the measurement results on two different levels: the first one, derives from the human factors affecting the event detection while the second one derives from the error rates of the classification–identification chain. In this paper, the focus is set on the latter, which has been called identification uncertainty. A model has been defined for its estimation and a methodology of application has been described. The results have been calculated for some specific situations in order to clarify the methodology and to have some estimations of the value of this contribution to uncertainty. Just for a location very close to the airport (aircraft events range over 20 dB), this contribution to uncertainty can be up to 0.5 dB when simple detection techniques are used, and can be reduced to approximately 0.1 dB when radar tracking is used to enhance the identification task. In more complex acoustic environments, the identification uncertainty can increase up to 5 dB (or more) in the absence of accurate classification/identification tools.