Relation between loudness and annoyance over time: Implications for assessing the perception of low-frequency noise

The literature suggests that, in contrast to loudness, annoyance increases over time. However, in these early measurements the annoyance exposure time usually did not exceed 120 s. In the current work, this temporal interval was extended to 3600 s (1 h). Within this time frame, both loudness and annoyance of low-frequency noise spectra containing dominant tones were measured at 12 temporal intervals by the method of successive magnitude estimation. Four noise spectra that evoked the largest annoyance-to-loudness ratios in previous reports were selected as stimuli. On average, after 1 h loudness declined by 8% and annoyance declined by 12.5% at moderate sensation levels (SL). By comparison, at 27-dB SL annoyance initially exceeded loudness by 51% up to 120 s and then, declined with time more slowly than loudness. These results indicate that, despite an 11-phon decrease in loudness level, the annoyance of a low-frequency steady noise with dominant tones below 50 Hz may initially increase over time. The annoyance increase may then be followed by a gradual annoyance decrease that mirrors the loudness decrease but at a slower rate. Taken together, the obtained relations imply, in accord with other data, that annoyance is not solely loudness based.