Spatial Knowledge via Auditory Information for Blind Individuals: Spatial Cognition Studies and the Use of Audio-VR.

Spatial cognition is a daily life ability, developed in order to be able to understand and interact with our environment. Even if all the senses are involved in mental representation of space elaboration, the lack of vision makes it more difficult, especially because of the importance of peripheral information in updating the relative positions of surrounding landmarks when one is moving. Spatial audio technology has long been used for studies of human perception, particularly in the area of auditory source localisation. The ability to reproduce individual sounds at desired positions, or complex spatial audio scenes, without the need to manipulate physical devices has provided researchers with many benefits. We present a review of several studies employing the power of spatial audio virtual reality for research in spatial cognition with blind individuals. These include studies investigating simple spatial configurations, architectural navigation, reaching to sounds, and sound design for improved acceptability. Prospects for future research, including those currently underway, are also discussed.

Auditory perception stability evaluation comparing binaural and loudspeaker Ambisonic presentations of dynamic virtual concert auralizations.

Auralizations can be computed in a variety of ways as well as be rendered over different sound reproduction systems. They are used as a design tool in architectural projects and for fundamental studies on spatial perception and cognition, hence requiring reliability and confidence in the obtained results. This study assessed this reliability through auditory perception stability by comparing the perceived differences between two rendering systems for a given set of second-order Ambisonic auralizations: virtual loudspeaker binaural rendering over head-tracked headphones versus 32-loudspeaker rendering. Anechoic extracts of jazz pieces have been recorded and presented in various acoustic conditions over these two systems, evaluated on the following criteria: Readability, distance, listener envelopment (LEV), apparent source width (ASW), reverberance, and loudness. Results show that consistent significant differences between scene conditions are comparably perceived across the two systems. However, significant effects of the sound reproduction system were observed for ASW, LEV, and reverberance in some configurations.

Sensitivity analysis of pinna morphology on head-related transfer functions simulated via a parametric pinna model.

The head-related transfer function (HRTF) defines the acoustic path from a source to the two ears of a listener in a manner that is highly dependent on direction. This directional dependence arises from the highly individual morphology of the pinna, which results in complex reflections and resonances. While this notion is generally accepted, there has been little research on the importance of different structural elements of the pinna on the HRTF. A parametric three-dimensional ear model was used to investigate the changes in shape of the pinna in a systematic manner with a view to determining important contributing morphological parameters that can be used for HRTF individualization. HRTFs were simulated using the boundary element method. The analysis comprised objective comparisons between the directional transfer function and diffuse field component. The mean spectral distortion was used for global evaluation of HRTF similarity across all simulated positions. A perceptual localization model was used to determine correspondences between perceptual cues and objective parameters. A reasonable match was found between the modelled perceptual results and the mean spectral distortion. Modifications to the shape of the concha were found to have an important impact on the HRTF, as did those in proximity to the triangular fossa. Furthermore, parameters that control the relief of the pinna were found to be at least as important as more frequently cited side-facing parameters, highlighting limitations in previous morphological/HRTF studies.

Potential Impact of C-STAT for Prehospital Stroke Triage up to 24 Hours on a Regional Stroke System.

Background and Purpose: Thrombectomy for large vessel occlusion acute ischemic stroke (AIS-LVO) may benefit patients up to 24 hour since last known normal (LKN). Prehospital tools, like the Cincinnati Stroke Triage Assessment Tool (C-STAT), are used to select hospital destination for suspected AIS-LVO patients. The objective of this study was to estimate the potential impact of the expanded thrombectomy time window on suspected AIS-LVO cases transported to the regional comprehensive stroke center (CSC). Methods: From June to November 2015, C-STAT was performed by prehospital providers following a positive prehospital Cincinnati Prehospital Stroke Scale (CPSS) stroke screen in suspected stroke/TIA patients. There was no preferential triage based on C-STAT results. Final diagnoses, including the presence of AIS-LVO was ascertained via medical record review. Impact of positive C-STAT cases on CSC volumes was estimated for up to 24 hours since LKN. Results: Of 158 patients with prehospital suspicion for stroke/TIA, 105 were CPSS positive within 24 hours of onset and had complete C-STAT and clinical data available for analysis. Forty-six percent (17/37) of C-STAT + were non-strokes. C-STAT sensitivity and specificity for LVO were 71% (95% CI 36-92) and 67% (95% CI 58-80), respectively. C-STAT triage would increase transport of prehospital suspected stroke cases to the CSC by 11% (12/105) within six hours and 21% (22/105) within 24 hours. Of 37 C-STAT + patients, only 5 (13.5%) had LVO as final diagnosis. Conclusions: Preferential triage of prehospital suspected stroke patients using C-STAT would increase the number of patients transported to the CSC by 11% within six hours and an additional 10% from six to 24 hours. For every patient with LVO as final diagnosis, approximately an additional 6 non-LVO patients would be triaged to a CSC.

Forum-Pre-Sabine room acoustic assumptions on reverberation and their influence on room acoustic design.

With his work on the Fogg Art Museum and Boston Symphony Hall between 1895 and 1900, Wallace C. Sabine laid a foundation for the field of architectural acoustics as a science. Prior to that, architects employed various quantifiable notions in acoustic design. Previous studies have reviewed metric guidelines based on the directivity of the human voice, which was utilized in at least 11 rooms in pre-Sabine times. Others studies have reviewed pre-Sabine design guidelines that were based on the quantification of the perception threshold between direct sound and first order reflections and which were followed in several rooms with acoustical performance needs. As the first studies concerned the direct sound and the second set concerned first order reflections, this study reviews opinions and knowledge regarding the later part of the acoustic response, also known as reverberation, during the 19th century. This effort brings to light a room acoustic design evolution showing why concert halls at the end of the 19th century mainly had surface finishes of wood and plaster as well as limited ceiling heights. While not equal to Sabine's thoroughness and completeness, numerous early experimental and theoretical reverberation approaches were found to hint at similar notions with both qualitative and quantitative efforts.

Comparison of direct and indirect perceptual head-related transfer function selection methods.

When a personalized set of head-related transfer functions (HRTFs) is not available, a common solution is identifying a perceptually appropriate substitute from a database. There are various approaches to this selection process whether based on localization cues, subjective evaluations, or anthropomorphic similarities. This study investigates whether HRTF rankings that stem from different selection methods yield comparable results. A perceptual study was carried out using a basic source localization method and a subjective quality judgment method for a common set of eight HRTFs. HRTF rankings were determined according to different metrics from each method for each subject and the respective results were compared. Results indicate a significant and positive mean correlation between certain metrics. The best HRTFs selected according to one method had significant above-average rating scores according to metrics in the second method.

Evaluation of a Computer-Based HIV Education Program for Adults Living with HIV.

This study evaluated a computer-delivered HIV and antiretroviral treatment education program in adults (N = 102) living with detectable HIV viral loads (> 200 copies/mL). The self-paced program provided immediate feedback for responses and financial incentives for responding correctly. The program was divided into three courses and a test of content from all three courses was delivered before and after participants completed each course. Test scores on the content delivered in Courses 1, 2 and 3 improved only after participants completed training on the relevant course. Initial test scores were positively correlated with health literacy and academic achievement; were negatively correlated with viral load; and were lowest for participants living in poverty. Education, academic achievement, and health literacy were related to how much participants learned following each course. Computer-based education is a convenient, effective approach to promoting an understanding of HIV and its treatment.

Auralization uses in acoustical design: A survey study of acoustical consultants.

While auralization technology is used in a variety of fields, particularly in architectural acoustics, there is a lack of data on the auralization tools used and actual practices. In this perspective, this work presents the results of a survey study on auralization uses in the acoustical design and consulting community, targeting acoustical consultants. The objectives are (1) to identify the tools and methods used by acousticians to create auralizations as well as effective uses so as to understand the benefits and changes provided by this technology, and (2) to highlight the difficulties and limitations linked to the use of auralizations in concrete projects. Based on the theory of acceptability and use of technology, the study was conducted from a mix of quantitative and qualitative data collection approaches, combining a questionnaire answered by 74 respondents with semi-directed interviews with nine practitioners. Results highlight the main uses of auralizations, the diversity of projects in which auralizations are applied, and how auralizations are currently used in real-world situations. The benefits of using this technology, inherent weaknesses in the tools, and practical difficulties are also discussed.

An archeoacoustic study of the history of the Palais du Trocadero (1878-1937).

During the 17th, 18th, and 19th centuries, a room acoustic theory arose with design goal to avoid echoes from occurring by quantifying the perception threshold between direct sound and 1st-order reflections. The room acoustic design of the large 19th century concert hall Palais du Trocadero (1878-1937) was based on this theory. As the resulting acoustics were notoriously poor, an attempt was undertaken in 1909 to correct the acoustics by installing additional absorbing material following the same "echo theory" design approach. In order to study the consequences of this design theory, four configurations of this concert hall have been numerically reconstructed. Through calibrated simulations, it was shown that in the case of the Palais du Trocadero, design decisions based on "echo theory" had a positive effect on the acoustics; however, due to the many curved surfaces, echoes, and sound focusing, the acoustic conditions remained poor.

Pre-Sabine room acoustic design guidelines based on human voice directivity.

With the work of Wallace C. Sabine on the lecture hall of the Fogg Art Museum and concert hall of Boston Symphony Hall, a foundation for the field of architectural acoustics as a science was laid between 1895 and 1900. Prior to that, architects employed various notions in acoustic design. Previous studies by the authors have reviewed 18th and 19th century design guidelines that were based on the quantification of the perception threshold between direct sound and first order reflections, with these guidelines being followed in the design of several rooms with acoustical demands. This study reviews an alternate metric guideline, based on the directivity and propagation distance of the human voice, which was utilized in several halls also during the 18th and 19th centuries. The related acoustic experiments tested how far sound was perceivable towards the front, sides, and rear of a speaking person. These ratios were used in the acoustical design of at least five lecture halls, four theater halls, one opera hall, and one concert hall, constructed in Germany, England, and the USA. These historic designs, and comparisons to modern measures and guidelines, are reviewed.

Estimated Impact of Emergency Medical Service Triage of Stroke Patients on Comprehensive Stroke Centers: An Urban Population-Based Study.

BACKGROUND AND PURPOSE: The American Stroke Association recommends that Emergency Medical Service bypass acute stroke-ready hospital (ASRH)/primary stroke center (PSC) for comprehensive stroke centers (CSCs) when transporting appropriate stroke patients, if the additional travel time is ≤15 minutes. However, data on additional transport time and the effect on hospital census remain unknown. METHODS: Stroke patients ≥20 years old who were transported from home to an ASRH/PSC or CSC via Emergency Medical Service in 2010 were identified in the Greater Cincinnati area population of 1.3 million. Addresses of all patients' residences and hospitals were geocoded, and estimated travel times were calculated. We estimated the mean differences between the travel time for patients taken to an ASRH/PSC and the theoretical time had they been transported directly to the region's CSC. RESULTS: Of 929 patients with geocoded addresses, 806 were transported via Emergency Medical Service directly to an ASRH/PSC. Mean additional travel time of direct transport to the CSC, compared with transport to an ASRH/PSC, was 7.9±6.8 minutes; 85% would have ≤15 minutes added transport time. Triage of all stroke patients to the CSC would have added 727 patients to the CSC's census in 2010. Limiting triage to the CSC to patients with National Institutes of Health Stroke Scale score of ≥10 within 6 hours of onset would have added 116 patients (2.2 per week) to the CSC's annual census. CONCLUSIONS: Emergency Medical Service triage to CSCs based on stroke severity and symptom duration may be feasible. The impact on stroke systems of care and patient outcomes remains to be determined and requires prospective evaluation.

Prospective Prehospital Evaluation of the Cincinnati Stroke Triage Assessment Tool.

BACKGROUND AND PURPOSE: A simple, easily adoptable scale with good performance characteristics is needed for EMS providers to appropriately triage suspected stroke patients to comprehensive stroke centers (CSC). Many existing tools are complex, require substantial training, or have not been prospectively validated in the prehospital setting. We describe the feasibility and effectiveness of prehospital implementation of our previously retrospectively derived and validated Cincinnati Stroke Triage Assessment Tool (C-STAT) to identify subjects with severe stroke (NIHSS ≥15) among all prehospital patients with clinical suspicion of stroke/TIA. Secondarily, we evaluated the tool's ability to identify subjects with NIHSS ≥10, large vessel occlusion (LVO), or needing services available only at a CSC. METHODS: Without formalized training, Cincinnati Fire Department providers performed standard stroke screening ("face, arm, speech, time;" FAST) and C-STAT as part of their assessment of suspected stroke/TIA patients. Outcomes for patients brought to the region's only CSC or assessed by the regional stroke team were determined through structured chart review by a stroke team nurse. C-STAT test characteristics for each outcome were calculated with 95% confidence intervals. RESULTS: Complete prehospital and outcome data were available for 58 FAST-positive subjects among 158 subjects with prehospital suspicion for stroke/TIA. Subjects were excluded if FAST was negative (n = 22), FAST or C-STAT was incompletely documented (n = 24), if the patient was taken to a non-CSC and did not receive a stroke team consult (n = 48), or if outcome data were missing (n = 6). C-STAT sensitivity and specificity for each outcome were: NIHSS ≥ 15, 77% (95% CI 46-95) and 84% (95% CI 69-93); NIHSS ≥10, 64% (95% CI 41-83) and 91% (95% CI 76-98); LVO, 71% (95% CI 29-96) and 70% (95% CI 55-83); overall CSC need 57% (95% CI 34-78) and 79% (95% CI 61-91). CONCLUSION: In this pilot prospective evaluation performed in the prehospital setting by EMS providers without formalized training, C-STAT is comparable to other published tools in test characteristics and may inform appropriate CSC triage beyond LVO ascertainment alone.

Identification of perceptually relevant methods of inter-aural time difference estimation.

The inter-aural time difference (ITD) is a fundamental cue for human sound localization. Over the past decades several methods have been proposed for its estimation from measured head-related impulse response (HRIR) data. Nevertheless, inter-method variations in ITD calculation have been found to exceed the known just noticeable differences (JNDs), leading to possible perceptible artifacts in virtual binaural auditory scenes, when personalized HRIRs are being used. In the absence of an objective means for validating ITD estimations, this paper examines which methods lead to the most perceptually relevant results. A subjective lateralization study compared objective ITDs to perceptually evaluated inter-aural pure delay offsets. Results clearly indicate the first-onset threshold detection method, using a low relative threshold of -30 dB, applied on 3 kHz low-pass filtered HRIRs as consistently the most perceptually relevant procedure across various metrics. Several alternative threshold values and methods based on the maximum or centroid of the inter-aural cross correlation of similarly filtered HRIR or HRIR envelopes also provided reasonable results. On the contrary, phase-based methods employing the integrated relative group delay or auditory model were not found to perform as well.

The influence of visual distance on the room-acoustic experience of auralizations.

Auralizations have become more prevalent in architectural acoustics and virtual reality. Studies have shown that by employing a methodical calibration procedure, ecologically/perceptually valid auralizations can be obtained. Another study demonstrated a manner to include dynamic voice directivity with results indicating these auralizations were judged significantly more plausible than auralizations with static source orientations. With the increased plausibility of auralizations, it is possible to study room-acoustic experience employing virtual reality, having confidence that the results also apply to real-life situations. Limited studies have examined the influence of visuals on room-acoustic experience. Using a virtual reality framework, this study investigated the influence of visuals on the room-acoustic experience of auralizations. Evaluations compared dynamic voice auralizations coherently matched with visualization positions to incoherently matched audio-visual pairs. Based on the results, the test population could be divided into three subgroups: (1) those who judged auralizations more acoustically distant with increased visual distance, (2) those who judged auralizations louder with increased visual distance, and (3) those whose audio judgment was uninfluenced by the visual stimulus.

Influence of head tracking on the externalization of speech stimuli for non-individualized binaural synthesis.

Binaural reproduction aims at recreating a realistic audio scene at the ears of the listener using headphones. In the real acoustic world, sound sources tend to be externalized (that is, perceived to be emanating from a source out in the world) rather than internalized (that is, perceived to be emanating from inside the head). Unfortunately, several studies report a collapse of externalization, especially with frontal and rear virtual sources, when listening to binaural content using non-individualized Head-Related Transfer Functions (HRTFs). The present study examines whether or not head movements coupled with a head tracking device can compensate for this collapse. For each presentation, a speech stimulus was presented over headphones at different azimuths, using several intermixed sets of non-individualized HRTFs for the binaural rendering. The head tracker could either be active or inactive, and the subjects could either be asked to rotate their heads or to keep them as stationary as possible. After each presentation, subjects reported to what extent the stimulus had been externalized. In contrast to several previous studies, results showed that head movements can substantially enhance externalization, especially for frontal and rear sources, and that externalization can persist once the subject has stopped moving his/her head.

Nitrogen Source Inventory and Loading Tool: An integrated approach toward restoration of water-quality impaired karst springs.

Nitrogen (N) from anthropogenic sources has contaminated groundwater used as drinking water in addition to impairing water quality and ecosystem health of karst springs. The Nitrogen Source Inventory and Loading Tool (NSILT) was developed as an ArcGIS and spreadsheet-based approach that provides spatial estimates of current nitrogen (N) inputs to the land surface and loads to groundwater from nonpoint and point sources within the groundwater contributing area. The NSILT involves a three-step approach where local and regional land use practices and N sources are evaluated to: (1) estimate N input to the land surface, (2) quantify subsurface environmental attenuation, and (3) assess regional recharge to the aquifer. NSILT was used to assess nitrogen loading to groundwater in two karst spring areas in west-central Florida: Rainbow Springs (RS) and Kings Bay (KB). The karstic Upper Floridan aquifer (UFA) is the source of water discharging to the springs in both areas. In the KB study area (predominantly urban land use), septic systems and urban fertilizers contribute 48% and 22%, respectively, of the estimated total annual N load to groundwater 294,400 kg-N/yr. In contrast for the RS study area (predominantly agricultural land use), livestock operations and crop fertilizers contribute 50% and 13%, respectively, of the estimated N load to groundwater. Using overall groundwater N loading rates for the KB and RS study areas, 4.4 and 3.3 kg N/ha, respectively, and spatial recharge rates, the calculated groundwater nitrate-N concentration (2.1 mg/L) agreed closely with the median nitrate-N concentration (1.7 mg/L) from groundwater samples in agricultural land use areas in the RS study area for the period 2010-2014. NSILT results provide critical information for prioritizing and designing restoration efforts for water-quality impaired springs and spring runs affected by multiple sources of nitrogen loading to groundwater. The calculated groundwater N concentration for the KB study area (1.45 mg/L) was approximately three times higher than the median N concentration (0.45 mg/L) for wells located in urban land use areas.

Correction method for averaging slowly time-variant room impulse response measurements.

Various methods exist for room acoustic measurements. To increase the signal-to-noise-ratio (SNR), averaging of repeated room impulse responses (RIR) can be performed under the assumption of time-invariant systems. Associated with a study of the Paris Notre Dame cathedral, time-variances due to minute temperature changes were observed which confounded results of averaged RIRs, producing significantly shorter reverberation times. A correction method for such time-variance of the acoustic system is proposed, based on time-stretching. Following correction, reverberation times of averaged RIRs were comparable to expected tolerance ranges for measurements, well within one just noticeable difference, while also exhibiting a mid-frequency SNR gain of 8 dB.

Perceptual attributes for the comparison of head-related transfer functions.

The benefit of using individual head-related transfer functions (HRTFs) in binaural audio is well documented with regards to improving localization precision. However, with the increased use of binaural audio in more complex scene renderings, cognitive studies, and virtual and augmented reality simulations, the perceptual impact of HRTF selection may go beyond simple localization. In this study, the authors develop a list of attributes which qualify the perceived differences between HRTFs, providing a qualitative understanding of the perceptual variance of non-individual binaural renderings. The list of attributes was designed using a Consensus Vocabulary Protocol elicitation method. Participants followed an Individual Vocabulary Protocol elicitation procedure, describing the perceived differences between binaural stimuli based on binauralized extracts of multichannel productions. This was followed by an automated lexical reduction and a series of consensus group meetings during which participants agreed on a list of relevant attributes. Finally, the proposed list of attributes was then evaluated through a listening test, leading to eight valid perceptual attributes for describing the perceptual dimensions affected by HRTF set variations.

Perceptive and objective evaluation of calibrated room acoustic simulation auralizations.

Recently, auralizations have become more prevalent in architectural acoustics and virtual reality. However, there have been few studies examining the perceptual quality achievable by room acoustic simulations and auralizations. Such studies have highlighted potential problems in creating perceptually equivalent simulations when compared to measured auralizations in terms of parameter estimation. In order to accomplish realistic auralizations, calibration of the geometrical acoustics model can be considered a necessary step. In situations where the studied space exists, well-calibrated auralizations can be employed for multiple purposes, such as multi-modal virtual reality explorations, studies of the acoustical influence of renovations, and historic research. Using this case type as a base, a perceptual study evaluating state-of-the-art binaural auralizations has been carried out. Three test sites of different complexity and acoustics were selected: the abbey church Saint-Germain-des-Prés, the cathedral Notre-Dame de Paris, and the Théâtre de l'Athénée. Models were calibrated according to omni-directional source-receiver measurements for reverberation and clarity parameters. In the subjective listening test, measured and simulated binaural auralizations were compared according to eight acoustic perceptual attributes. Results showed that the methodical calibration procedure employed in combination with attention to control factors led to ecologically/perceptually valid auralizations.

Gender and Time to Arrival among Ischemic Stroke Patients in the Greater Cincinnati/Northern Kentucky Stroke Study.

BACKGROUND: Some studies of stroke patients report longer prehospital delays in women, but others conflict; studies vary in their inclusion of factors including age and stroke severity. We aimed to investigate the relationship between gender and time to emergency department (ED) arrival and the influence of age and stroke severity on this relationship. METHODS: Ischemic stroke patients 20 years old or older who presented to 15 hospitals within a 5-county region of Greater Cincinnati/Northern Kentucky during 2010 were included. Time from symptom onset to ED arrival and covariates were abstracted by study nurses and reviewed by study physicians. Data were analyzed using logistic regression with time to arrival dichotomized at 3 hours or less in the overall sample and then stratified by National Institutes of Health Stroke Scale (NIHSS) and age. RESULTS: 1991 strokes (55% women) were included. Time to arrival was slightly longer in women (geometric mean 337 minutes [95% confidence interval {CI} 307-369] versus 297 [95% CI 268-329], P = .05), and 24% of women versus 27% of men arrived within 3 hours (P = .15). After adjusting for age, race, NIHSS, living situation, and other covariates, gender was not associated with delayed time to arrival (OR = 1.00, 95% CI .78-1.28). This did not change across age or NIHSS categories. CONCLUSIONS: After adjusting for factors including age, NIHSS score, and living alone, women and men with ischemic stroke had similar times to arrival. Arrival time is not likely a major contributor to differences in outcome between men and women.