The Technology Of Binaural Listening

This book reports on the application of advanced models of the human binaural hearing system in modern technology, among others, in the following areas: binaural analysis of aural scenes, binaural de-reverberation, binaural quality assessment of audio channels, loudspeakers and performance spaces, binaural perceptual coding, binaural processing in hearing aids and cochlea implants, binaural systems in robots, binaural/tactile human-machine interfaces, speech-intelligibility prediction in rooms and/or multi-speaker scenarios. An introduction to binaural modeling and an outlook to the future are provided. Further, the book features a MATLAB toolbox to enable readers to construct their own dedicated binaural models on demand.

This book offers a computational framework for modeling active exploratory listening that assigns meaning to auditory scenes. Understanding auditory perception and cognitive processes involved with our interaction with the world are of high relevance for a vast variety of ICT systems and applications. Human beings do not react according to what they perceive, but rather, they react on the grounds of what the percepts mean to them in their current action-specific, emotional and cognitive situation. Thus, while many models that mimic the signal processing involved in human visual and auditory processing have been proposed, these models cannot predict the experience and reactions of human users. This book presents a model that incorporates both signal-driven (bottom-up), and hypothesis-driven (top-down) processing.

Sound, devoid of meaning, would not matter to us. It is the information sound conveys that helps the brain to understand its environment. Sound and its underlying meaning are always associated with time and space. There is no sound without spatial properties, and the brain always organizes this information within a temporal–spatial framework. This book is devoted to understanding the importance of meaning for spatial and related further aspects of hearing, including cross-modal inference. People, when exposed to acoustic stimuli, do not react directly to what they hear but rather to what they hear means to them. This semiotic maxim may not always apply, for instance, when the reactions are reflexive. But, where it does apply, it poses a major challenge to the builders of models of the auditory system. Take, for example, an auditory model that is meant to be implemented on a robotic agent for autonomous search-&-rescue actions. Or think of a system that can perform judgments on the sound quality of multimedia-reproduction systems. It becomes immediately clear that such a system needs • Cognitive capabilities, including substantial inherent knowledge • The ability to integrate information across different sensory modalities To realize these functions, the auditory system provides a pair of sensory organs, the two ears, and the means to perform adequate preprocessing of the signals provided by the ears. This is realized in the subcortical parts of the auditory system. In the title of a prior book, the term Binaural Listening is used to indicate a focus on sub-cortical functions. Psychoacoustics and auditory signal processing contribute substantially to this area. The preprocessed signals are then forwarded to the cortical parts of the auditory system where, among other things, recognition, classification, localization, scene analysis, assignment of meaning, quality assessment, and action planning take place. Also, information from different sensory modalities is integrated at this level. Between sub-cortical and cortical regions of the auditory system, numerous feedback loops exist that ultimately support the high complexity and plasticity of the auditory system. The current book concentrates on these cognitive functions. Instead of processing signals, processing symbols is now the predominant modeling task. Substantial contributions to the field draw upon the knowledge acquired by cognitive psychology. The keyword Binaural Understanding in the book title characterizes this shift. Both books, The Technology of Binaural Listening and the current one, have been stimulated and supported by AABBA, an open research group devoted to the development and application of models of binaural hearing. The current book is dedicated to technologies that help explain, facilitate, apply, and support various aspects of binaural understanding. It is organized into five parts, each containing three to six chapters in order to provide a comprehensive overview of this emerging area. Each chapter was thoroughly reviewed by at least two anonymous, external experts. The first part deals with the psychophysical and physiological effects of Forming and Interpreting Aural Objects as well as the underlying models. The fundamental concepts of reflexive and reflective auditory feedback are introduced. Mechanisms of binaural attention and attention switching are covered—as well as how auditory Gestalt rules facilitate binaural understanding. A general blackboard architecture is introduced as an example of how machines can learn to form and interpret aural objects to simulate human cognitive listening. The second part, Configuring and Understanding Aural Space, focuses on the human understanding of complex three-dimensional environments—covering the psychological and biological fundamentals of auditory space formation. This part further addresses the human mechanisms used to process information and interact in complex reverberant environments, such as concert halls and forests, and additionally examines how the auditory system can learn to understand and adapt to these environments. The third part is dedicated to Processing Cross-Modal Inference and highlights the fundamental human mechanisms used to integrate auditory cues with cues from other modalities to localize and form perceptual objects. This part also provides a general framework for understanding how complex multimodal scenes can be simulated and rendered. The fourth part, Evaluating Aural-scene Quality and Speech Understanding, focuses on the object-forming aspects of binaural listening and understanding. It addresses cognitive mechanisms involved in both the understanding of speech and the processing of nonverbal information such as Sound Quality and Quality-of- Experience. The aesthetic judgment of rooms is also discussed in this context. Models that simulate underlying human processes and performance are covered in addition to techniques for rendering virtual environments that can then be used to test these models. The fifth part deals with the Application of Cognitive Mechanisms to Audio Technology. It highlights how cognitive mechanisms can be utilized to create spatial auditory illusions using binaural and other 3D-audio technologies. Further, it covers how cognitive binaural technologies can be applied to improve human performance in auditory displays and to develop new auditory technologies for interactive robots. The book concludes with the application of cognitive binaural technologies to the next generation of hearing aids.

The field of spatial hearing has exploded in the decade or so since Jens Blauert's classic work on acoustics was first published in English. This revised edition adds a new chapter that describes developments in such areas as auditory virtual reality (an important field of application that is based mainly on the physics of spatial hearing), binaural technology (modeling speech enhancement by binaural hearing), and spatial sound-field mapping. The chapter also includes recent research on the precedence effect that provides clear experimental evidence that cognition plays a significant role in spatial hearing.The remaining four chapters in this comprehensive reference cover auditory research procedures and psychometric methods, spatial hearing with one sound source, spatial hearing with multiple sound sources and in enclosed spaces, and progress and trends from 1972 (the first German edition) to 1983 (the first English edition) -- work that includes research on the physics of the external ear, and the application of signal processing theory to modeling the spatial hearing process. There is an extensive bibliography of more than 900 items.

In this work the importance of individualization in binaural technique is investigated. The results extend the present knowledge on the efficient measurement of individual head-related transfer functions (HRTFs) and highlight the importance of individual equalization filters in binaural reproduction, using both loudspeakers and headphones. Moreover, an integrated framework for the calculation of such equalization filters is presented. An innovative measurement setup was developed to allow the fast acquisition of individual HRTFs. The hardware was designed to be compatible with the range extrapolation technique. An individual HRTF dataset with 4000 directions can be measured in less than 6 minutes with this new setup. A framework was presented that integrates causality constraints to the regularized frequency domain calculation of crosstalk cancellation (CTC) filter. This framework also addresses the switching of active loudspeakers applying a weighted filter calculation method. A sound localization test showed that individualized CTC systems provide performance similar to that of binaural listening while nonindividualized CTC systems provide a significantly lower localization performance. Finally, a robust individual headphone equalization method was proposed. Perceptual tests showed that, in all but one of the tested situations, no audible differences between the original sound source and its binaural auditory display could be perceived.

The field of Binaural Hearing involves studies of auditory perception, physiology, and modeling, including normal and abnormal aspects of the system. Binaural processes involved in both sound localization and speech unmasking have gained a broader interest and have received growing attention in the published literature. The field has undergone some significant changes. There is now a much richer understanding of the many aspects that comprising binaural processing, its role in development, and in success and limitations of hearing-aid and cochlear-implant users. The goal of this volume is to provide an up-to-date reference on the developments and novel ideas in the field of binaural hearing. The primary readership for the volume is expected to be academic specialists in the diverse fields that connect with psychoacoustics, neuroscience, engineering, psychology, audiology, and cochlear implants. This volume will serve as an important resource by way of introduction to the field, in particular for graduate students, postdoctoral scholars, the faculty who train them and clinicians.

The current popular and scientific interest in virtual environments has provided a new impetus for investigating binaural and spatial hearing. However, the many intriguing phenomena of spatial hearing have long made it an exciting area of scientific inquiry. Psychophysical and physiological investigations of spatial hearing seem to be converging on common explanations of underlying mechanisms. These understandings have in turn been incorporated into sophisticated yet mathematically tractable models of binaural interaction. Thus, binaural and spatial hearing is one of the few areas in which professionals are soon likely to find adequate physiological explanations of complex psychological phenomena that can be reasonably and usefully approximated by mathematical and physical models. This volume grew out of the Conference on Binaural and Spatial Hearing, a four-day event held at Wright-Patterson Air Force Base in response to rapid developments in binaural and spatial hearing research and technology. Meant to be more than just a proceedings, it presents chapters that are longer than typical proceedings papers and contain considerably more review material, including extensive bibliographies in many cases. Arranged into topical sections, the chapters represent major thrusts in the recent literature. The authors of the first chapter in each section have been encouraged to take a broad perspective and review the current state of literature. Subsequent chapters in each section tend to be somewhat more narrowly focused, and often emphasize the authors' own work. Thus, each section provides overview, background, and current research on a particular topic. This book is significant in that it reviews the important work during the past 10 to 15 years, and provides greater breadth and depth than most of the previous works.

Hearing is dependent on neural processing of acoustic cues obtained by the left and right ears. Neural signals driven by the two ears are integrated at multiple levels of the central auditory system, which enables animals including humans to perform various functions including localization of a sound source. A natural listening environment typically contains sounds from multiple sources. These sounds can have different spectral and temporal features and occur at either the same or different time. Integration can happen among neural signals elicited by the same or different sounds. The way of integration can greatly affect how individual sounds are sensed and perceived. Functions such as auditory grouping and stream segregation, which are central to establishing coherent auditory images in a complex listening environment, are highly dependent on the way of integration. Binaural hearing is complicated by individual differences and developmental changes in head and pinna shape/size as binaural cues can be affected by these differences and changes. Furthermore, neural processing of binaural cues can be influenced by hearing impairments and the use of hearing aids and cochlear implants. These factors likely require a listener to optimize the use of binaural cues through learning and to use plastic changes in the nervous system to perform the optimization. Great strides have been made in understanding binaural processing in normal and impaired auditory systems. This Research Topic aims to highlight some of the latest findings in the following areas: 1) Animal behavioral and human psychoacoustical studies of binaural hearing; 2) Neural encoding and processing of binaural cues and structural as well as neurophysiological bases of such encoding and processing; 3) Contribution of binaural neural processing to auditory functions such as sound-source localization, binaural fusion, binaural interference, spatial release from masking, auditory grouping, and auditory stream segregation; 4) Computational models of binaural processing; 5) Learning and plastic changes in binaural processing following hearing loss or alterations of acoustic environment and structural as well as physiological bases of these behavioral changes; 6) Clinical aspects of binaural processing including application of processing strategies, including research on the benefits of bilateral cochlear implantation, and the neural correlates thereof