This slim volume is one in the “SpringerBriefs” series. True to form, it has 79 pages, is a paperback, and covers much of the work in auditory interfaces up to about 2014. The authors are from the Faculty of Electrical Engineering at the University of Ljubljana, in Slovenia.

The authors concentrate

on a special group of auditory interfaces using spatial sound for the representation of information. The addition of information on the location of a selected sound source or group of sources shows many advantages over a mere single-channel audio. This survey explains the most important limitations of the human hearing system and the perception of spatial sound.

Chapter 1 is a brief introduction to the field and an explanation of the authors’ goals in the writing of this book.

Chapter 2 discusses the spatial characteristics of sound waves. It starts off with a review of the physics and physiological characteristics of sound and the human body, beginning with Poisson’s equation and sound intensity and proceeding to audio perception and psychoacoustics. The main business of the localization of sound is begun in Section 2.3. This explains the phenomenon of how humans are capable of localizing the source or sources of sound even when blindfolded, by considering the intensity, relative delay, and pitch of the sound sources. The generation of test sources and measurement of head-related impulse responses (HRIR) follows, along with a description of some standard sources and public depositories of such sources.

Chapter 3, “Auditory Interfaces,” shows various types of output to and input from computers. These have become very important in our age of mobile devices where our eyes have to be directed fully on our paths. Texting while driving is known to be a very dangerous practice, and although speaking while driving is not without its own perils, it is safer than texting. Even walking while using mobile devices comes with risks of bumping into other pedestrians or lamp poles. Both text-to-speech synthesis and automatic speech recognition are discussed here.

Chapter 4 summarizes some of the more important research reports about spatial auditory interfaces in several different contexts. The first of these is portable devices and music players. As portable devices get smaller and smaller, the amount of space allocated to the screen and the keyboard gets less and less. That means that it is both difficult to read the screen and difficult to respond to it using fingers alone. Experiments show that vocal input can be used to successfully command and control these devices.

The second report is about teleconferencing. For distributed meetings and some types of gaming, some form of virtual acoustical environment is created. It has been found that if individual participants share this environment with each member assured of a unique spatial location for voice and location within that space, the meeting is more productive.

Several experimental systems for implementing virtual reality (VR) and augmented reality (AR) are described next. These may or may not require earphones, headsets, special gloves, or other specialized equipment. VR is now entering the commercial market and may become very important in the near future.

The fourth report introduces aircraft uses. The existing traffic collision avoidance systems (TCASs) alert the cockpit of potential collision possibilities, and it was found that if azimuthal information was added to the system, then the pilot’s reaction time in visually identifying an approaching aircraft was significantly improved.

Use with ordinary automobiles appears next. As with aircraft, auditory signals with azimuthal spatial information attached can significantly aid the driver in avoiding collisions. Other information-rich audio interfaces that include pitch and harmonics are sometimes useful but can introduce errors in judgment if misinterpreted.

Chapter 6 describes a few results when the technology is used with the visually impaired. Directional information about physical location and proximity is coarsely digitized and encoded into a series of sequential changes in pitch. These encodings must then be learned by the visually impaired subjects. The experimenters have reported that the systems are quite usable, and after the training period the users are actually able to “see” the world around them.

The last section discusses experiments where a stimulus from the external world is inserted directly into the brain without passing through visual or aural devices. Since our movements are caused by electrical signals passing through our nervous system, sending electrical pulses directly into our brains represents a potentially useful stimulus. So far the studies have shown that these approaches are rather limited due to their low accuracy and dependability. Work is continuing.

The standard of English used throughout is excellent, although the style is a little dry. The main weakness is a dearth of examples from the commercial sector. There is much to be learned from a study of these systems where the user interface is all-important.

The subject is very specialized and the authors do a good job with it. Scientists and developers in the field of audio human-computer interfaces will find this book a good up-to-date summary of the state of the art.