What is considered a significant change in relation to Part 150 noise studies?

In the context of Part 150 noise studies, a significant change in noise levels is defined as an increase of 1.5 dB or more. This threshold is established based on the Federal Aviation Administration's criteria for assessing noise impacts around airports. The reasoning behind the choice of 1.5 dB lies in research indicating that changes of this magnitude are generally detectable by the human ear and can affect community perception of noise levels.

This cutoff reflects a balance between the scientific understanding of noise impact and the practical implications for noise mitigation measures. It alerts stakeholders, including airport authorities and local communities, about potential increases in noise that could warrant further investigation or action to mitigate noise concerns. Changes below this level are typically considered minor and may not result in significant community impact, rarely necessitating new studies or mitigation plans.