The role of early and late reflections on perception of source orientation

Abstract

Sound radiation of most natural sources, like human speakers or musical instruments, typically exhibits a spatial directivity pattern. This directivity contributes to the perception of sound sources in rooms, affecting the spatial energy distribution of early reflections and late diffuse reverberation. Thus, for convincing sound field reproduction and acoustics simulation, source directivity has to be considered. Whereas perceptual effects of directivity, such as source-orientation-dependent coloration, appear relevant for the direct sound and individual early reflections, it is unclear how spectral and spatial cues interact for later reflections. Better knowledge of the perceptual relevance of source orientation cues might help to simplify the acoustics simulation. Here, it is assessed as to what extent directivity of a human speaker should be simulated for early reflections and diffuse reverberation. The computationally efficient hybrid approach to simulate and auralize binaural room impulse responses [Wendt et al., J. Audio Eng. Soc. 62, 11 (2014)] was extended to simulate source directivity. Two psychoacoustic experiments assessed the listeners' ability to distinguish between different virtual source orientations when the frequency-dependent spatial directivity pattern of the source was approximated by a direction-independent average filter for different higher reflection orders. The results indicate that it is sufficient to simulate effects of source directivity in the first-order reflections.

Perceptual Matching of Room Acoustics for Auditory Augmented Reality in Small Rooms - Literature Review and Theoretical Framework

“…The addition of further reflections did not cause additional localization shifts, only smoothed the transition. Similar observations were obtained by Steffens et al (2021). Early reflections also influence other spatial aspects than the apparent location of the sound source (Bech, 1998).…”

“…If the loudspeaker was turned by 180∘, facing away from the listener, the plausibility was seriously affected, if the same approach was used (Neidhardt, 2021). This confirms the findings by Zotter & Frank (2015); Steffens et al (2021) and shows that auralizations created by the various signal processing approaches should be tested with such an indirect reproduction scenario because it is much more critical than the listening positions in front of a sound source.…”

Perceptual Significance of Tone-Dependent Directivity Patterns of Musical Instruments

“…If the listeners were positioned in the same direction as the microphone with which the melodies were recorded, then the only directivity that could be heard would be due to early reflections and late reverberation. It was shown in [35] that early reflections are significant for detecting the orientation of a sound source. The results of the present study suggest that subjects were more successful in differentiating the variants of the directivity tested in this study.…”

Modular Room Simulation for the IVES 3D Engine

“…The ISM module calculates the positions of the image sources by mirroring the original sound source as a 3D point on each wall as a plane. As a compromise between computational efficiency and a perceptually sufficient degree of spatial details, only first-order reflections are computed [16,17]. The positions of the image sources result in corresponding delays and attenuations of the original signal in relation to the position and distance to the receiver/listener.…”