Effects of Spatial Speech Presentation on Listener Response Strategy for Talker-Identification

Abstract

This study investigates effects of spatial auditory cues on human listeners' response strategy for identifying two alternately active talkers ("turn-taking" listening scenario). Previous research has demonstrated subjective benefits of audio spatialization with regard to speech intelligibility and talker-identification effort. So far, the deliberate activation of specific perceptual and cognitive processes by listeners to optimize their task performance remained largely unexamined. Spoken sentences selected as stimuli were either clean or degraded due to background noise or bandpass filtering. Stimuli were presented via three horizontally positioned loudspeakers: In a non-spatial mode, both talkers were presented through a central loudspeaker; in a spatial mode, each talker was presented through the central or a talker-specific lateral loudspeaker. Participants identified talkers via speeded keypresses and afterwards provided subjective ratings (speech quality, speech intelligibility, voice similarity, talker-identification effort). In the spatial mode, presentations at lateral loudspeaker locations entailed quicker behavioral responses, which were significantly slower in comparison to a talker-localization task. Under clean speech, response times globally increased in the spatial vs. non-spatial mode (across all locations); these "response time switch costs," presumably being caused by repeated switching of spatial auditory attention between different locations, diminished under degraded speech. No significant effects of spatialization on subjective ratings were found. The results suggested that when listeners could utilize task-relevant auditory cues about talker location, they continued to rely on voice recognition instead of localization of talker sound sources as primary response strategy. Besides, the presence of speech degradations may have led to increased cognitive control, which in turn compensated for incurring response time switch costs.

Keywords: response strategy; sound localization; spatial auditory attention; spatial auditory cues; speech perception; switch costs; talker-identification; voice recognition.

Figure 1

Test layout deployed in the present study. The listener sits at a table, facing an array of three left (L), central (C), and right (R) loudspeakers (L = −30°, C = 0°, R = 30° azimuth) at a distance of approximately 2.15 m. The listener responds to stimuli by pressing keys on a response pad, while fixating a white cross displayed on a monitor screen below C. This figure originally appeared in Uhrig et al. (2020a), copyright 2020, with permission from IEEE.

Figure 2

Three continuous rating scales were employed for subjective assessment of perceived speech quality (top scale), speech intelligibility (top scale), voice similarity (middle scale), and talker-identification effort (bottom scale). A seven-point “extended continuous scale” design was implemented in accordance with ITU-T Recommendation P.851 (2003). Another version of this figure originally appeared in Uhrig et al. (2020a), copyright 2020, with permission from IEEE.

Figure 3

Effects of presentation mode and speech degradation on rating for evaluative (speech quality, speech intelligibility) and task-related [voice similarity, talker-identification (TI) effort] attributes of overall listening experience. The numeric range of the y-axis (1–7) corresponds to scale labels shown in Figure 2. Error bars represent 95% confidence intervals. Another version of this figure originally appeared in Uhrig et al. (2020a), copyright 2020, with permission from IEEE.

Figure 4

Effects of presentation mode and speech degradation on correct response time. Error bars represent 95% confidence intervals. Another version of this figure originally appeared in Uhrig (2022), copyright 2021, with permission from Springer.

Figure 5

Effects of speech degradation and loudspeaker location on correct response time in the spatial_id mode. Color-shaded bars represent 95% confidence ranges for the non-spatial_id mode under different speech degradation levels (i.e., black bar = non-spatial_id/clean, purple bar = non-spatial_id/noisy, green bar = non-spatial_id/filtered), as depicted in Figure 4. Diamond-shaped points represent the spatial_loc mode (talker-localization task). Error bars represent 95% confidence intervals. The dashed horizontal line at 700 ms marks the lower y-axis limit in Figure 4, for better comparability. Another version of this figure originally appeared in Uhrig (2022), copyright 2021, with permission from Springer.

Figure 6

Effects of loudspeaker location, spatial block (spatial block 1, spatial block 2, spatial block 3), and lateral trial half (first trial half, second trial half) on correct response time. Error bars represent 95% confidence intervals. Another version of this figure originally appeared in Uhrig (2022), copyright 2021, with permission from Springer.

Figure 7

Effects of presentation mode and speech degradation on correct response rate in the spatial_id mode. Open square-shaped points represent the non-spatial_id mode only (involving presentations only at the central loudspeaker location). Error bars represent 95% confidence intervals.