Spatial Audio Cues Research Articles

EEG alpha and pupil diameter reflect endogenous auditory attention switching and listening effort.

Everyday environments often contain distracting competing talkers and background noise, requiring listeners to focus their attention on one acoustic source and reject others. During this auditory attention task, listeners may naturally interrupt their sustained attention and switch attended sources. The effort required to perform this attention switch has not been well studied in the context of competing continuous speech. In this work, we developed two variants of endogenous attention switching and a sustained attention control. We characterized these three experimental conditions under the context of decoding auditory attention, while simultaneously evaluating listening effort and neural markers of spatial‐audio cues. A least‐squares, electroencephalography (EEG)‐based, attention decoding algorithm was implemented across all conditions. It achieved an accuracy of 69.4% and 64.0% when computed over nonoverlapping 10 and 5‐s correlation windows, respectively. Both decoders illustrated smooth transitions in the attended talker prediction through switches at approximately half of the analysis window size (e.g., the mean lag taken across the two switch conditions was 2.2 s when the 5‐s correlation window was used). Expended listening effort, as measured by simultaneous EEG and pupillometry, was also a strong indicator of whether the listeners sustained attention or performed an endogenous attention switch (peak pupil diameter measure [ p=0.034] and minimum parietal alpha power measure [ p=0.016]). We additionally found evidence of talker spatial cues in the form of centrotemporal alpha power lateralization ( p=0.0428). These results suggest that listener effort and spatial cues may be promising features to pursue in a decoding context, in addition to speech‐based features.

Exploiting spatial audio cues for pilot navigation in degraded visual environments

Aviation mishaps resulting from degraded visual environments (DVEs) represent a significant loss in military personnel and aircraft every year. DVEs are considered any type of environmental condition (e.g., sand, snow, or fog) that visually obstructs the pilot and can cause spatial disorientation. The current study represents a tri-service effort exploring the implementation of spatial audio cueing techniques to aid pilot navigation in DVEs. Directional cueing (i.e., indicating the location of target waypoints) was achieved by spatializing an auditory stimulus using the SoundLab audio rendering package and convolving audio signals with (non-individualized) head-related transfer functions. Two spatial cue conditions were tested, either rendered dynamically in reference to the pilot’s head via head tracking or with respect to aircraft heading. Data were collected from pilots operating a full-motion UH-60 Black Hawk flight simulator at the U.S. Army Aeromedical Research Laboratory. Pilots performed multiple flight maneuvers, such as a “turn to target” localization task, a "side-step" maneuver positioning the aircraft over a stationary target, and an “approach to moving target” task. Performance was assessed by measures of localization error, completion time, and failure rate. Findings from this study provide information on sensory cueing display countermeasures for helicopter flight in DVEs.

Spatialized audio improves call sign recognition during multi-aircraft control

We investigated the impact of a spatialized audio display on response time, workload, and accuracy while monitoring auditory information for relevance. The human ability to differentiate sound direction implies that spatial audio may be used to encode information. Therefore, it is hypothesized that spatial audio cues can be applied to aid differentiation of critical versus noncritical verbal auditory information. We used a human performance model and a laboratory study involving 24 participants to examine the effect of applying a notional, automated parser to present audio in a particular ear depending on information relevance. Operator workload and performance were assessed while subjects listened for and responded to relevant audio cues associated with critical information among additional noncritical information. Encoding relevance through spatial location in a spatial audio display system--as opposed to monophonic, binaural presentation--significantly reduced response time and workload, particularly for noncritical information. Future auditory displays employing spatial cues to indicate relevance have the potential to reduce workload and improve operator performance in similar task domains. Furthermore, these displays have the potential to reduce the dependence of workload and performance on the number of audio cues.

Current Use and Future Perspectives of Spatial Audio Technologies in Electronic Travel Aids

Electronic travel aids (ETAs) have been in focus since technology allowed designing relatively small, light, and mobile devices for assisting the visually impaired. Since visually impaired persons rely on spatial audio cues as their primary sense of orientation, providing an accurate virtual auditory representation of the environment is essential. This paper gives an overview of the current state of spatial audio technologies that can be incorporated in ETAs, with a focus on user requirements. Most currently available ETAs either fail to address user requirements or underestimate the potential of spatial sound itself, which may explain, among other reasons, why no single ETA has gained a widespread acceptance in the blind community. We believe there is ample space for applying the technologies presented in this paper, with the aim of progressively bridging the gap between accessibility and accuracy of spatial audio in ETAs.

Improving 3-D Audio Localisation Through the Provision of Supplementary Spatial Audio Cues

This study examined whether azimuth localising performance for non-individualised 3-D audio without integrated head tracking can be improved through the provision of supplementary reference signals. Twenty-two participants attempted to determine the location of spatial sounds developed through a non-individualised head-related transfer function (HRTF) while performing a visual distractor task. Localising sounds were randomly presented at 0- degrees elevation for each 10-degree increment about the azimuth. Three audio conditions were tested, two of which included different supplementary cues in the form of stationary and transient sounds that were spatially positioned to aid localising reference toward the midsagittal plane and interaural axis. The supplementary cues decreased errors in front- back perception; however, they did not significantly aid azimuth localising performance, and occasionally were reported to distract and disorient some participants. Supplementary audio cues have the potential to improve localising performance but should be more closely associated with the presented sound to lessen distraction and disorientation.

Semantic Versus Spatial Audio Cues: Is There a Downside to Semantic Cueing?

An auditory spatial Stroop paradigm was used to examine the effects of semantic and spatial audio cue conflict on accuracy and response time. Participants responded to either the semantic meaning or the spatial location of a directional word, which was either congruent (i.e. the word “right” being presented from the right) or incongruent (i.e. the word “right” being presented from the left). Contrary to our predictions, people responded more accurately to the semantic meaning of the directional words relative to spatial audio cues. An interaction between task type and congruency indicated people found it more difficult to ignore the semantic content of the word when performing the location version of this task relative to ignoring the location in the semantic task. Implications of these results for use in driver collision-avoidance warning systems are discussed. The current results indicate that performance benefits gained by the use of directional words in combination with spatial audio may be offset by greater detriment to performance when the warning system presents unreliable or incongruent semantic information.

Semantic versus Spatial Audio Cues: Is There a Downside to Semantic Cueing?

An auditory spatial Stroop paradigm was used to examine the effects of semantic and spatial audio cue conflict on accuracy and response time. Participants responded to either the semantic meaning or the spatial location of a directional word, which was either congruent (i.e. the word “right” being presented from the right) or incongruent (i.e. the word “right” being presented from the left). Contrary to our predictions, people responded more accurately to the semantic meaning of the directional words relative to spatial audio cues. An interaction between task type and congruency indicated people found it more difficult to ignore the semantic content of the word when performing the location version of this task relative to ignoring the location in the semantic task. Implications of these results for use in driver collision-avoidance warning systems are discussed. The current results indicate that performance benefits gained by the use of directional words in combination with spatial audio may be offset by greater detriment to performance when the warning system presents unreliable or incongruent semantic information.

In-Flight Navigation Using Head-Coupled and Aircraft-Coupled Spatial Audio Cues

A flight test was conducted to evaluate how effectively spatialized audio cues could be used to maneuver a general aviation aircraft through a complex navigation course. Two conditions were tested: a head-coupled condition, where audio cues were updated in response to changes in the orientation of the pilot's head, and an aircraft-coupled condition, where audio cues were updated in response to changes in the direction of the aircraft. Both cueing conditions resulted in excellent performance, with the pilots on average passing within 0.25 nm of the waypoints on the navigation course. However, overall performance was better in the aircraft-coupled condition than in the head-coupled condition. This result is discussed in terms of an alignment mismatch between the pilot's frame of reference and that of the aircraft, which is critical when using spatial audio to cue the desired orientation of the vehicle rather than the location of an object in space.

Spatial information displays on a wearable computer

Increasing portability of computing power marks a broad emerging trend in advanced human-computer interaction. Wearable computers, the next generation of portable machines, worn on the body, provide constant access to computing and communications resources. However, wide adoption of wearable computers first requires solving unique interface challenges. One of the most important is how to present and interact with information in a wearable environment. We designed and evaluated three methods for presenting information in a wearable environment. Subjects found spatial displays easier and more effective. Spatial audio and visual cues further enhanced performance.