Loudness-based noise metrics for annoyance to rotorcraft noise using Thurstone analysis

Annoyance to rotorcraft noise continues to be an area of concern to communities, and the question remains for researchers and regulators regarding which noise metrics best capture the perception to these types of vehicles. Traditional metrics based on A-weighting have not been supplanted, but metrics based on loudness (ISO 532-1) may offer improvements since they include signal processing closer to the human auditory system. In addition to loudness, sound quality metrics (sharpness, tonality, etc.) have also been found to correlate with annoyance. Using data collected in recent psychoacoustic tests on helicopter and urban air mobility vehicle noise, annoyance scales using Thurstone’s Law of Comparative Judgment account for the relationship between perception, which is an internal judgment, and the external perceptual response. This work also investigates correlations between noise metrics and annoyance for traditional noise metrics as well as for loudness-based metrics, including psychoacoustic annoyance models (e.g., Zwicker). This leads to a psychoacoustic annoyance model for urban air mobility vehicle noise that correlates better with annoyance than Zwicker’s model. Results also show that loudness-based metrics, integrated over time similarly to sound exposure level, are highly correlated with annoyance. Finally, Thurstone’s scale yields just-noticeable-differences in noise metrics for annoyance to rotorcraft noise.