A-weighted sound pressure level as an indicator of short-term loudness or annoyance of road-traffic sound

Two listening experiments were conducted in order to determine whether A-weighting is a valid indicator of the perceived loudness or annoyance of road-traffic sound. Because A-weighting has been criticized for not properly integrating energy at low frequencies, experimental road-traffic sounds were selected with a wide range in low-frequency content, assessed as the difference between C- and A-weighted sound pressure levels (LC−A). In the first experiment, 30 listeners assessed the perceived loudness of the selected sounds. In the second experiment, another group of 31 listeners assessed the perceived annoyance of the same sounds. Sounds with high levels of LC−A were louder and more annoying than sounds with medium levels of LC−A, which in turn were louder and more annoying than sounds with low levels of LC−A, at similar A-weighted sound pressure levels (LA). It was estimated that the change in perceived loudness or annoyance associated with a 1 dB change in LC−A would correspond to approximately a 0.4 dB change in LA. In contrast, sounds with similar Zwicker loudness levels (LN) were approximately equal in loudness and annoyance irrespective of their LC−A. Thus, LN was found to be superior to LA as an indicator of short-term loudness and annoyance of road-traffic sounds with wide variation in low-frequency content.