Practitioners’ Corner – Update Concerning ISO 9613-2

The 2024 revision of ISO 9613-2, widely used in Canada for environmental noise assessments, introduced changes to the barrier attenuation (Abar) and meteorological correction ( C met) algorithms. Comparisons with the 1996 edition show that the revised standard can predict sound levels up to 10 dB higher at long source–receiver distances, raising concerns about potential overprediction and its implications for regulatory compliance and mitigation costs. In response to feedback from practitioners and industry, the ISO working group has initiated an amendment that would temporarily restore the original formulations of Abar and C met while a longer-term solution is developed. This paper summarizes the concerns associated with the 2024 revision and outlines the ongoing ISO efforts to address them.