The annoyance caused by unpleasant low-frequency sound is known to be influenced by many factors, but studies of the influence of differences in such signals reaching a listener's two separate ears are not common. This is despite the fact that when such sound intrudes into indoor environments, the received binaurally incoherent low-frequency sound can exhibit values of Interaural Cross Correlation (IACC) that are reduced well below that measured in the free field, and are associated with clearly audible differences relative to similar signals that are more binaurally coherent. In this study, a selection of three unpleasant low-frequency sounds were submitted to chaotic amplitude modulation with three different peak modulation rates (2 Hz, 5 Hz and 10 Hz), and were presented as both coherent and incoherent signals via a laterally positioned pair of subwoofers. The results clearly revealed that binaural incoherence influences the unpleasantness of low frequency sound perceived by human listeners. The study also revealed that of the three peak modulation rates tested, the lowest rate (2 Hz) was associated with greater reported annoyance than that reported at the higher rates (5 Hz and 10 Hz).
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