Methodology for the evaluation of low-frequency environmental noise: a case-study

Abstract

Industrial sources like open-cycle gas turbines, boilers, forced and induced draft fans, shakers on hoppers, vibratory screens, and compressors are just some of the possible sources of low-frequency environmental noise, as well as wind farms or surface transport infrastructures. However, unlike the latter, industrial sources are characterized by a so large variability of the components that constitute them to require specific studies on the modalities of emission and on the effects induced to the receptors.In the near future, the evaluation and control of low-frequency noise sources will become a key factor in environmental management, which requires specific knowledge, investigation strategies, and proper measurement techniques.In this paper an industrial plant held liable for low-frequency noise annoyance is analyzed, focusing on the benefits achievable by adopting an investigation strategy combining simultaneous indoor and outdoor noise measurements carried out along with vibration and weather data acquisition. The specific investigation methodology applied to the case study analyzed highlighted the importance of validating the acoustic data through a thorough analysis of the meteorological data, focusing on effects on sound pressure level variation due to strong wind (gusts). The role of preliminary structured interviews to people claiming to be annoyed and the importance of their written notes during unattended monitoring sessions are also addressed.