The effect of sound incidence angle on loudness was investigated using real sound sources positioned in an anechoic chamber. Eight normal-hearing listeners produced loudness matches between a frontal reference location and seven sources placed at other directions, both in the horizontal and median planes. Matches were obtained via a two-interval, adaptive forced-choice (2AFC) procedure for three center frequencies (0.4, 1, and ) and two overall levels (45 and SPL). The results showed that loudness is not constant over sound incidence angles, with directional sensitivity varying over a range of up to , exhibiting considerable frequency dependence, but only minor effects of overall level. The pattern of results varied substantially between subjects, but was largely accounted for by variations in individual head-related transfer functions. Modeling of binaural loudness based on the at-ear signals favored a sound-power summation model, according to which the maximum binaural gain is only , over competing models based on larger gains, or on the summation of monaural loudness indices.
Directional loudness in an anechoic sound field, head-related transfer functions, and binaural summationa)
Ville Pekka Sivonen, Wolfgang Ellermeier; Directional loudness in an anechoic sound field, head-related transfer functions, and binaural summation. J. Acoust. Soc. Am. 1 May 2006; 119 (5): 2965–2980. https://doi.org/10.1121/1.2184268
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