Just-noticeable-differences for annoyance to lightweight helicopter flyovers

Noise certification standards for helicopters only include a small number of simple maneuvers. However, normal helicopter operations include a large variety of maneuvers, which may lead to a large variety of noise levels and a large variety of annoyance responses. As a result, a helicopter that is type certified may still produce noise levels that are perceived as annoying during normal operations. Specifically, noise certification metrics are not intended to track subtle yet important differences in annoyance perception, especially for the variety of sounds associated with different helicopter maneuvers. A psychoacoustic test is carried out to measure the variation in annoyance to helicopter maneuvers of equal A-weighted Sound Exposure Level (SEL). Results show that helicopter noises of equal SEL are not equal in terms of annoyance. A subset of helicopter noise stimuli are presented at higher or lower SEL, allowing changes in annoyance to be associated with changes in SEL and other metrics. Results show high correlation between annoyance and conventional, time-integrated noise certification metrics like SEL and Effective Perceived Noise Level (EPNL) but also between annoyance and newer loudness-based metrics. Just-noticeable-differences in these metrics are calculated and show how much a metric must change to result in 75% agreement in the annoyance difference. Annoyance to helicopter maneuvers is highly variable, but the limits of this variation are discussed and quantified in relation to just-noticeable-differences.