Working with the ISO/PAS 1996-3:2018 Impulsive Standard with Application to Industry and Windfarms Using Long-term Monitoring Data

Abstract

ISO/PAS 1996-3:2018 provides a method to objectively calculate an adjustment to the measured \(L_{{{\text{Aeq}},T}}\) sound level for impulsive sound during the measurement period T. The method given in ISO 1996-3 states that measurements are to be made where possible at such times that impulsive sound from sources of residual sound is not present as these can impact the assessment of the source of specific sound under investigation. It recommends that impulsive sound that is suspected of being caused by sources of residual sound is to be excluded from analysis. It is common when conducting a noise survey at receptors which are located some distance from an intrusive noise source using long-term monitoring data that residual sound, such as from traffic, aircraft, birds, and insects, is a significant noise contributor. The impulsive adjustments derived according to ISO 1996-3 may therefore be applied inadvertently to the residual sound contrary to the recommendation in the Standard, if they are not identified and eliminated from the calculations by specific involvement of a person in the analysis. The method recommended in the Standard to minimise the influence of residual sound includes the examination of audio recordings or other methods of noise source identification on indicated impulse events and then uses the calculation method provided in the Standard with the recommended sample time interval of 10–25 ms to determine the impulse adjustment \(K_{I}\). An additional method is proposed in this paper based on selecting an appropriate value of the assessment time interval commensurate with the duration of single impulsive noise events being assessed as well as other observations relating to the implementation of ISO 1996-3 in both industry and windfarm noise assessments.