Ville Pekka Sivonen

Directional loudness in an anechoic sound field, head-related transfer functions, and binaural summation.

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 5 kHz) and two overall levels (45 and 65 dB SPL). The results showed that loudness is not constant over sound incidence angles, with directional sensitivity varying over a range of up to 10 dB, 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 3 dB, over competing models based on larger gains, or on the summation of monaural loudness indices.

Directional loudness and binaural summation for wideband and reverberant sounds.

In an earlier investigation [Sivonen and Ellermeier, J. Acoust. Soc. Am. 119, 2965-2980 (2006)], the effect of sound incidence angle on loudness was investigated for anechoic, narrowband sounds. In the present follow-up investigation, the effect of incidence angle on loudness was investigated using wideband sounds under anechoic conditions and narrowband sounds under reverberant conditions. Five listeners matched the loudness of a sound coming from five incidence angles in the horizontal plane to that of the same sound with frontal incidence. These directional loudness matches were obtained with an adaptive, two-alternative, two-interval, forced-choice procedure. The stimuli were presented to the listeners via individual binaural synthesis. The results show that loudness depends on sound incidence angle in both experiments. The wideband and reverberant sounds, however, yielded significantly smaller directional effects than had been obtained for the same listeners when anechoic, narrowband sounds were used. When modeling the binaural summation underlying the loudness matches, a power summation of the at-ear signals yielded good predictions for all types of stimuli investigated.

Directional loudness of narrow‐band noises in an anechoic sound field

In order to investigate the effect of sound incidence angle on loudness across a larger set of parameters than have been used in most previous studies, a listening experiment was carried out using a loudspeaker setup in an anechoic chamber. Eight subjects, whose absolute hearing thresholds and head‐related transfer functions (HRTFs) were measured, participated in a total of 22 sessions each. On each trial their task was to judge which of two narrow‐band noises sounded louder. These judgments were used in an adaptive procedure to find loudness matches between a frontal reference location and seven other sources, positioned both in the horizontal and median planes. Sound incidence angle, center frequency, and overall SPL were varied in the procedure. The results show that loudness is not constant over sound incidence angles, with matches varying over a range of 10 dB, and showing considerable frequency dependency. The pattern of results also varies substantially between subjects, but can be accounted for by...