Recording and Analysis of Head Movements, Interaural Level and Time Differences in Rooms and Real-World Listening Scenarios

The science of how we use interaural differences to localise sounds has been studied for over a century and in many ways is well understood. But in many of these psychophysical experiments listeners are required to keep their head still, as head movements cause changes in interaural level and time differences (ILD and ITD respectively). But a fixed head is unrealistic. Here we report an analysis of the actual ILDs and ITDs that occur as people naturally move and relate them to gyroscope measurements of the actual motion. We used recordings of binaural signals in a number of rooms and listening scenarios (home, office, busy street etc). The listener's head movements were also recorded in synchrony with the audio, using a micro-electromechanical gyroscope. We calculated the instantaneous ILD and ITDs and analysed them over time and frequency, comparing them with measurements of head movements. The results showed that instantaneous ITDs were widely distributed across time and frequency in some multi-source environments while ILDs were less widely distributed. The type of listening environment affected head motion. These findings suggest a complex interaction between interaural cues, egocentric head movement and the identification of sound sources in real-world listening situations

Realidad Virtual Acústica: El Abordaje de las Redes Neuronales Artificiales

This work presents a new approach to obtain the Binaural Impulse Responses (BIRs) for an auralization system by using a committee of artificial neuronal networks (ANNs). The proposed method is capable to reconstruct the desired modified Head Related Impulse Responses (HRIRs) by means of spectral modification and spatial interpolation. In order to cover the entire auditory reception space, without increasing the network’s architecture complexity, a structure with multiple RNAs (committee) was adopted, where each network operates in la specific reception region (bud). The modeling error, in the frequency domain, is investigated considering the logarithmic nature of the human hearing. It was observed that the proposed methodology obtained a computational gain of approximately 62%, in terms of processing time reduction, compared to the classical signal processing method used to obtain auralizations.The applicability of the new method in auralization systems is validated by comparative analysis of the results, which includes the BIR’s generation and calculation of one binaural acoustic parameter (IACF), showing very low magnitude errors. En este trabajo se presenta un nuevo abordaje para obtener las respuestas impulsivas biauriculares (BIRs) para un sistema de aurilización utilizando un conjunto de redes neuronales artificiales (RNAs). El método propuesto es capaz de reconstruir las respuestas impulsivas asociadas a la cabeza humana (HRIRs) por medio de modificación espectral y de interpolación espacial. Para poder cubrir todo el espacio auditivo de recepción, sin aumentar la complejidad de la arquitectura de la red, una estructura con varias RNAs (conjunto) fue adoptada, donde cada red opera en una región específica del espacio (gomo). El error de modelaje en el dominio de la frecuencia es investigado considerando la naturaleza logarítmica de la audición humana. A través de la metodología propuesta se obtuvo un ahorro del tiempo de procesamiento computacional de aproximadamente 62% en relación al método tradicional de procesamiento de señales utilizado para aurilización. La aplicabilidad del nuevo método en sistemas de aurilización es reforzada mediante un análisis comparativo de los resultados, que incluyen la generación de las BIRs y el cálculo de un parámetro acústico biauricular (IACF), los cuales muestran errores con magnitudes reducidas

3D Sound applied to the design of Assisted Navigation Devices for the Visually Impaired

This work presents an approach to generate 3D sound by using a set of artificial neural networks (ANNs). The proposed method is capable to reconstruct the Head Related Impulse Responses (HRIRs) by means of spatial interpolation. In order to cover the whole reception auditory space, without increasing the network complexity, a structure of multiple networks (set), each one modeling a specific area was adopted. The three main factors that influence the model accuracy --- the network's architecture, the reception area's aperture angles and the HRIR's time shifts --- are investigated and an optimal setup is presented. The computational effort to process the ANN is shown to be slightly smaller than traditional interpolation methods and all error calculation reached very low levels, validating the method to be used in the design of a 3D sound emitter capable of provide navigation aid for the visually impaired. Two approaches are presented in order to detect obstacles, one which makes use of computational vision techniques and other with laser proximity sensors. Este trabajo presenta un abordaje para generar sonido 3D utilizando un conjunto de redes neuronales artificiales (RNAs). El método propuesto es capaz de reconstruir la Respuestas Impulsivas Asociadas a Cabeza Humana (HRIRs) mediante interpolación espacial. Con el fin de cubrir todo el espacio de recepción auditivo, sin aumentar la complejidad de la red, fue adoptada una estructura de múltiples redes (conjunto), cada una modelando un área específica. Los tres factores principales que influyen en la exactitud del modelo --- la arquitectura de la red, ángulos de apertura de la zona de recepción y los cambios de tiempo del HRIR --- son investigados y es presentada una configuración óptima. El esfuerzo computacional necesario para procesar la RNA muestra ser menor que métodos tradicionales de interpolación y todos los cálculos de error alcanzan niveles muy bajos, validando el método para ser utilizado en el diseño de un emisor de sonido 3D capaz de proporcionar asistencia en la navegación de discapacitados visuales. Dos enfoques se presentan con el fin de detectar obstáculos, uno que hace uso de técnicas de visión computacional y otro con sensores de proximidad de láser.&nbsp

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.This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement no. 643636.Peer Reviewe

Auditory Displays and Assistive Technologies: the use of head movements by visually impaired individuals and their implementation in binaural interfaces

Visually impaired people rely upon audition for a variety of purposes, among these are the use of sound to identify the position of objects in their surrounding environment. This is limited not just to localising sound emitting objects, but also obstacles and environmental boundaries, thanks to their ability to extract information from reverberation and sound reflections- all of which can contribute to effective and safe navigation, as well as serving a function in certain assistive technologies thanks to the advent of binaural auditory virtual reality. It is known that head movements in the presence of sound elicit changes in the acoustical signals which arrive at each ear, and these changes can improve common auditory localisation problems in headphone-based auditory virtual reality, such as front-to-back reversals. The goal of the work presented here is to investigate whether the visually impaired naturally engage head movement to facilitate auditory perception and to what extent it may be applicable to the design of virtual auditory assistive technology. Three novel experiments are presented; a field study of head movement behaviour during navigation, a questionnaire assessing the self-reported use of head movement in auditory perception by visually impaired individuals (each comparing visually impaired and sighted participants) and an acoustical analysis of inter-aural differences and cross- correlations as a function of head angle and sound source distance. It is found that visually impaired people self-report using head movement for auditory distance perception. This is supported by head movements observed during the field study, whilst the acoustical analysis showed that interaural correlations for sound sources within 5m of the listener were reduced as head angle or distance to sound source were increased, and that interaural differences and correlations in reflected sound were generally lower than that of direct sound. Subsequently, relevant guidelines for designers of assistive auditory virtual reality are proposed

A Framework for Site-Specific Spatial Audio Applications

As audio recording and reproduction technology has advanced over the past five decades, increasing attention has been paid to recreating the highly spatialised listening experience we understand from our physical environment. This is the logical next step in the quest for increasing audio clarity, particularly as virtual reality gaming and augmented reality experiences become more widespread. This study sought to develop and demonstrate a technical framework for the production of site-specific audio-based works that is user-friendly and cost effective. The system was intended to be used by existing content producers and audio programmers to work collaboratively with a range of site-based organisations such as museums and galleries to produce an audio augmentation of the physicality of the space. This research was guided by four key aims: 1. Demonstrate a compositional method for immersive spatial audio that references the novel physical environment and the listener’s movement within it. 2. Describe a framework for the development and deployment of a spatial audio visitor technology system. 3. Prototype a naturalistic method for the delivery and navigation of contextual information via audio. 4. Deploy, demonstrate, and evaluate a spatial audio experience within a representative environment. The resulting system makes use of a range of existing technologies to provide a development experience and output that meets a clearly defined set of criteria. Furthermore, a case study application has been developed that demonstrates the use of the system to augment a selection of six paintings in a gallery space. For each of these paintings, a creative spatial composition was produced that demonstrates the principles of spatial composition discussed in this thesis. A spoken informational layer sits on top of this acting as a museum audio guide, featuring navigation using head gestures for a hands-free experience. This thesis presents a detailed discussion of the artistic intentions and techniques employed in the production of the six soundscapes, as well as an evaluation of the resulting application in use in a public gallery space