Tonality Perception Lessons Learned 2023-01-1104

Tonality is an important quality of sound to consider in many applications because people are more sensitive to tonal sound than broad band sound. The future is expected to bring Advanced Air Mobility (AAM) vehicles, including small unmanned aerial systems (sUAS), urban air mobility (UAM) vehicles and regional air mobility (RAM) vehicles. These manned and unmanned vehicles are propelled by rotors. Rotors tend to generate tonal sound as their blades interact periodically with surrounding airflow features. Tonality is therefore relevant to AAM noise. In this paper several tonality metrics are examined for their ability to explain perceived annoyance of AAM flyover noise as measured by NASA’s Rotorcraft Sound Quality Metric 1 (ROQM-1) test. The various investigated metrics use one-third octave band, narrow band, and autocorrelation analysis. It is observed that tonality influences but does not control perceived flyover noise annoyance due to other sound qualities like roughness, consistent with previous work. The metrics are also examined for their ability to explain perceived tonality of sounds generated by IT equipment. The autocorrelation metrics are observed to best explain perceived tonality while also being among the best of the other metrics for explaining flyover annoyance. The plausibility of the auditory nerve(s) as a physiological auto-correlator is also discussed.