Effects of reverberation conditions and physical versus virtual source placement on localization in virtual sound environments

Sound field synthesis systems vary in number and arrangement of loudspeakers and methods used to generate virtual sound environments to study human hearing perception. While previous work has evaluated the accuracy with which these systems physically reproduce room acoustic conditions, less is known on assessing subjective perception of those conditions, such as how well such systems preserve source localization. This work quantifies the accuracy and precision of perceived localization from a multi-channel sound field synthesis system at Boys Town National Research Hospital, which used 24 physical loudspeakers and vector-based amplitude panning to generate sound fields. Short bursts of broadband speech-shaped noise were presented from source locations (either coinciding with a physical loudspeaker location, or panned between loudspeakers) under free-field and modeled reverberant-room conditions. Listeners used a HTC Vive remote laser tracking system to point to the perceived source location.Results show that the system synthesizes source locations accurately for both physical and panned sources, in both azimuth and elevation. Panned sources, though, are localized less precisely than physical sources. Reverberant condition is also found to affect both the accuracy and precision of localization in the azimuthal plane, with dry conditions producing greater accuracy and better precision. Only accuracy (not precision) of localization in elevation was impacted by reverberant condition, with reverberant cases producing results closer to the target than dry cases. An interaction effect of reverberant condition with elevation on localization in elevation, though, indicates that dry conditions result in better localization in elevation than reverberant ones at an elevation close to head height, but the situations at higher elevations are where subjects localized dry sources lower than the target height, while reverberant ones were more accurately placed. Other laboratories with sound field synthesis systems are encouraged to gather similar data on the accuracy and precision of localization in azimuth and elevation, so that results from studies using these systems can be better interpreted in light of the capabilities of the system to generate accurate and precise reproductions of source locations. [Work supported by NIH GM109023.] Advisor: Lily M. Wan