Investigating phoneme-dependencies of spherical voice directivity patterns II: Various groups of phonemes

Musical instruments as dynamic sound sources

Unlike electro-acoustic sound sources, musical instruments have a time-varying, dynamic directivity, due to the note-dependent radiation behavior of the instrument and due to the expressive movements that musicians perform with their instrument. While previous studies have generally examined the directivity of the static, unmoved instrument for specific notes played, we show the individual and combined contributions of these two factors to a temporal modulation of the radiation behavior, based on motion tracking of typical movement patterns for all instruments of a classical symphony orchestra and on the directivity measured for all partials over the entire pitch range of these instruments. The effect of this modulation, which is manifested by changes in timbre and room acoustic excitation, was determined by spectral variations in the free field and under reverberant conditions, as well as by a modulation of room acoustic parameters. Our results show that these effects are well above the just noticeable differences for all musical instruments and all perceptual variables considered. While the effect of motion dominates for brass instruments, string and woodwind instruments exhibit large note-related differences, which should be taken into account in virtual acoustic realities if an auditory liveliness comparable to physical reality is to be achieved.

Phoneme dependence of horizontal asymmetries in voice directivity

Human voice directivity shows horizontal asymmetries caused by the shape of the lips or the position of the tooth and tongue during vocalization. This study presents and analyzes the asymmetries of voice directivity datasets of 23 different phonemes. The asymmetries were determined from datasets obtained in previous measurements with 13 subjects in a surrounding spherical microphone array. The results show that asymmetries are inherent to human voice production and that they differ between the phoneme groups with the strongest effect on the [s], the [l], and the nasals [m], [n], and [ŋ]. The least asymmetries were found for the plosives.

Investigating phoneme-dependencies of spherical voice directivity patterns II: Various groups of phonemes

The substantial variation between articulated phonemes is a fundamental feature of human voice production. However, while the spectral and temporal aspects of the phonemes have been extensively studied, few have investigated the spatial aspects and analyzed phoneme-dependent differences in voice directivity. This paper extends our previous research focusing on the directivity patterns of selected vowels and fricatives [Pörschmann and Arend, J. Acoust. Soc. Am. 149(6), 4553-4564 (2021)] and examines different groups of phonemes, such as plosives, nasals, voiced alveolars, and additional fricatives. For this purpose, full-spherical voice directivity measurements were performed for 13 persons while they articulated the respective phonemes. The sound radiation was recorded simultaneously using a surrounding spherical microphone array with 32 microphones and then spatially upsampled to a dense sampling grid. Based on these upsampled datasets, the spherical voice directivity was studied, and phoneme-dependent variations were analyzed. The results show significant differences between the groups of phonemes. However, within three groups (plosives, nasals, and voiced alveolars), the differences are small, and the variations in the directivity index were statistically insignificant.