Effect of Environment-Related Cues on Auditory Distance Perception in the Context of Audio-Only Augmented Reality

Audio-only augmented reality consists of enhancing a real environment with virtual sound events. A seamless integration of the virtual events within the environment requires processing them with artificial spatialization and reverberation effects that simulate the acoustic properties of the room. However, in augmented reality, the visual and acoustic environment of the listener may not be fully mastered. This study aims to gain some insight into the acoustic cues (intensity and reverberation) that are used by the listener to form an auditory distance judgment, and to observe if these strategies can be influenced by the listener’s environment. To do so, we present a perceptual evaluation of two distance-rendering models informed by a measured Spatial Room Impulse Response. The choice of the rendering methods was made to design stimuli categories in which the availability and reproduction quality of acoustic cues are different. The proposed models have been evaluated in an online experiment gathering 108 participants who were asked to provide judgments of auditory distance about a stationary source. To evaluate the importance of environmental cues, participants had to describe the environment in which they were running the experiment, and more specifically the volume of the room and the distance to the wall they were facing. It could be shown that these context cues had a limited, but significant, influence on the perceived auditory distance.

Psychoacoustic Principle, Methods, and Problems with Perceived Distance Control in Spatial Audio

One purpose of spatial audio is to create perceived virtual sources at various spatial positions in terms of direction and distance with respect to the listener. The psychoacoustic principle of spatial auditory perception is essential for creating perceived virtual sources. Currently, the technical means for recreating virtual sources in different directions of various spatial audio techniques are relatively mature. However, perceived distance control in spatial audio remains a challenging task. This article reviews the psychoacoustic principle, methods, and problems with perceived distance control and compares them with the principles and methods of directional localization control in spatial audio, showing that the validation of various methods for perceived distance control depends on the principle and method used for spatial audio. To improve perceived distance control, further research on the detailed psychoacoustic mechanisms of auditory distance perception is required.

Preserving Human Perspectives in Cultural Heritage Acoustics: Distance Cues and Proxemics in Aural Heritage Fieldwork

We examine the praxis implications of our working definition of aural heritage: spatial acoustics as physically experienced by humans in cultural contexts; aligned with the aims of anthropological archaeology (the study of human life from materials). Here we report on human-centered acoustical data collection strategies from our project “Digital Preservation and Access to Aural Heritage via a Scalable, Extensible Method,” supported by the National Endowment for the Humanities (NEH) in the USA. The documentation and accurate translation of human sensory perspectives is fundamental to the ecological validity of cultural heritage fieldwork and the preservation of heritage acoustics. Auditory distance cues, which enable and constrain sonic communication, relate to proxemics, contextualized understandings of distance relationships that are fundamental to human social interactions. We propose that source–receiver locations in aural heritage measurements should be selected to represent a comprehensive range of proxemics according to site-contextualized spatial-use scenarios, and we identify and compare acoustical metrics for auditory distance cues from acoustical fieldwork we conducted using this strategy in three contrasting case-study heritage sites. This conceptual shift from architectural acoustical sampling to aural heritage sampling prioritizes culturally and physically plausible human auditory/sound-sensing perspectives and relates them to spatial proxemics as scaled architecturally.

On the influence of non-individual binaural cues and the impact of level normalization on auditory distance estimation of nearby sound sources

Nearby sound sources provide distinct binaural cues, mainly in the form of interaural level differences, which vary with respect to distance and azimuth. However, there is a long-standing controversy regarding whether humans can actually utilize binaural cues for distance estimation of nearby sources. Therefore, we conducted three experiments using non-individual binaural synthesis. In Experiment 1, subjects had to estimate the relative distance of loudness-normalized and non-normalized nearby sources in static and dynamic binaural rendering in a multi-stimulus comparison task under anechoic conditions. Loudness normalization was used as a plausible method to compensate for noticeable intensity differences between stimuli. With the employed loudness normalization, nominal distance did not significantly affect distance ratings for most conditions despite the presence of non-individual binaural distance cues. In Experiment 2, subjects had to judge the relative distance between loudness-normalized sources in dynamic binaural rendering in a forced-choice task. Below chance performance in this more sensitive task revealed that the employed loudness normalization strongly affected distance estimation. As this finding indicated a general issue with loudness normalization for studies on relative distance estimation, Experiment 3 directly tested the validity of loudness normalization and a frequently used amplitude normalization. Results showed that both normalization methods lead to remaining (incorrect) intensity cues, which subjects most likely used for relative distance estimation. The experiments revealed that both examined normalization methods have consequential drawbacks. These drawbacks might in parts explain conflicting findings regarding the effectiveness of binaural cues for relative distance estimation in the literature.

Audio-visual interactions in egocentric distance perception: Ventriloquism effect and aftereffect

The processes of audio-visual integration and of visually-guided re-calibration of auditory distance perception are not well understood. Here, the ventriloquism effect (VE) and aftereffect (VAE) were used to study these processes in a real reverberant environment. Auditory and audio-visual (AV) stimuli were presented, in interleaved trials, over a range of distances from 0.7 to 2.04 m in front of the listener, whose task was to judge the distance of auditory stimuli or of the auditory components of AV stimuli. The relative location of the visual and auditory components of AV stimuli was fixed within a session such that the visual component was presented from distance 30% closer (V-closer) than the auditory component, 30% farther (V-farther), or aligned (V-aligned). The study examined the strength of VE and VAE as a function of the reference distance and of the direction of the visual component displacement, and the temporal profile of the build-up/break-down of these effects. All observed effects were approximately independent of target distance when expressed in logarithmic units. The VE strength, measured in the AV trials, was roughly constant for both directions of visual-component displacement such that, on average, the responses shifted in the direction of the visual component by 72% of the audio-visual disparity. The VAE strength, measured on the interleaved auditory-only trials, was stronger in the V-farther than the V-closer condition (44% vs. 31% of the audio-visual disparity, respectively). The VAE persisted to post-adaptation auditory-only blocks of trials, however it was weaker and the V-farther/V-closer asymmetry was reduced. The rates of build-up/break-down of the VAE were also asymmetrical, with slower adaptation in the V-closer condition. These results suggest that, on a logarithmic scale, the AV distance integration is symmetrical, independent of the direction of induced shift, while the visually-induced auditory distance re-callibration is asymmetrical, stronger and faster when evoked by more distant visual stimuli.

Size–Distance Scaling With Absolute and Relative Auditory Distance Information

In the dynamic 3D space, it is critical for survival to perceive size of an object and rescale it with distance from an observer. Humans can perceive distance via not only vision but also audition, which plays an important role in the localization of objects, especially in visually ambiguous environments. However, whether and how auditory distance information contributes to visual size perception is not well understood. To address this issue, we investigated the efficiency of size–distance scaling by using auditory distance information that was conveyed by binaurally recorded auditory stimuli. We examined the effects of absolute distance information of a single sound sequence (Experiment 1) and relative distance information between two sound sequences (Experiment 2) on visual size estimation performances in darkened and well-lit environments. We demonstrated that humans could perform size–distance disambiguation by using auditory distance information even in darkness. Curiously, relative distance information was more efficient in size–distance scaling than absolute distance information, suggesting a high reliance on relative auditory distance information in our visual spatial experiences. The results highlight a benefit of audiovisual interaction for size–distance processing and calibration of external events under visually degraded situations.

Patient-Centered Medical Home With Colocation: Observations and Insights From an Academic Family Medicine Clinic

There is a movement in the United States to transform family medicine practices from single physician–based patient care to team-based care. These teams are usually composed of multiple disciplines, including social workers, pharmacists, registered nurses, physician assistants, nurse practitioners, and physicians. The teams support patients and their families, provide holistic care to patients of all ages, and allow their members to work to the highest level of their training in an integrated fashion. Grouping care team members together within visual and auditory distance of each other is likely to enhance communication and teamwork, resulting in more efficient care for patients. This grouping is termed colocation. The authors describe how the use of colocation can lead to clearer, faster communication between care team members. This practice style has the potential to be expanded into various clinical settings in any given health system and to almost all clinical specialties and practices.

Effects of interpersonal familiarity on the auditory distance perception of level-equalized reverberant speech

Familiarity with sound sources is known to have a modulatory effect on auditory distance perception. However, the level of familiarity that can affect distance perception is not clearly understood. A subjective experiment that aims to investigate the effects of interpersonal familiarity on auditory distance perception with level-equalized stimuli is reported. The experiment involves a binaural listening task where different source distances between 0.5 and 16 m were emulated by convolving dry speech signals with measured binaural room impulse responses. The experimental paradigm involved level-equalized stimuli comprising speech signals recorded from different-gender couples who have self-reported to have known each other for more than a year with daily interaction. Each subject judged the distances of a total of 15 different speech stimuli from their partner as well as spectrally most similar and most dissimilar strangers, for six different emulated distances. The main finding is that a similar but unfamiliar speaker is localized to be further away than a familiar speaker. Another finding is that the semantic properties of speech can potentially have a modulating effect on auditory distance judgements.