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Description An illusion of auditory space can be generated by the appropriate filtering of sounds presented over headphones: the so-called virtual auditory space VAS. This book provides a bridge between many of the different disciplines that are involved in developing and exploiting this technology. The first part is fairly introductory in nature, while the second examines a number of issues relating to the generation of high fidelity virtual auditory space.
The last two chapters review current research applications of VAS. Product details Format Paperback pages Dimensions x x Other books in this series. Cytokines in the Nervous System Nancy J. Add to basket. Cannabinoids Vincenzo Di Marzo. Sleep and Sleep Disorders: Malcolm Lader. From Messengers to Molecules Gernot Riedel. Table of contents 1. Share This Paper.
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Virtual Auditory Space: Generation and Applications
Figures and Tables. Citations Publications citing this paper. McAnally , Russell L. Martin , Jason B. Virtual, Augmented and Mixed Reality. The sonel mapping acoustical modeling method Bill Kapralos. Jin , Simon Carlile.
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References Publications referenced by this paper. Distribution of errors in auditory localisation. S Carlile , P Leong , a. Consistent with this idea, it has been known for some time that, when a sound stimulus is of a duration that permits small head movements, multiple sampling of the sound field increases the localization performance, particularly in the context of resolving front-back confusions Wightman and Kistler, ; see also Brimijoin and Akeroyd, More recently, the integration of self-motion information has also been shown to play an important role in the perception of an externalized sound source Brimijoin et al.
At a theoretical level, it has recently been demonstrated that an auditory spatial representation can be established purely on the basis of audio-motor information. In a very important modeling study Aytekin et al. Over many pairs of movements and samples, the system built up an ordered list of the HRTF pairs that corresponded to the many different possible orientations from which the HRTFs were originally recorded.
Other sensory-motor models of auditory localization have been subsequently developed e. Such models may provide a basis for understanding how auditory localization develops in the congenitally blind or how the mature auditory system is able to retune to spectral localization cues in the absence of visual input. In the previous work showing accommodation to ear molds, we and others have found that there is a significant range of individual differences in both the extent and range of accommodation.
Some subjects appear to asymptote in performance after a couple of weeks of wearing the molds, while others continue to improve over 4 or 5 weeks. Similarly, while most subjects show performance changes that approach their pre-mold, control levels, others improve far less Hofman et al. Such difference could reflect individual differences in the capacity of the auditory system to adapt, although, given the relative homogeneity of the subject pool we feel this is unlikely.
Taking the latter case first, acoustically related accommodation changes could result from differences in the extent of the distortion of the spectral cues produced by each mold. While the molds all looked fairly similar in size and shape, this is consistent with the large acoustic impact of relatively small differences in the sizes and shapes of normal outer ears Figure 1 ; e. In addition, the extent of performance improvements due to accommodation is also likely to be dependent on the spatial quality of the residual cues.
For instance, near complete abolition of directionally dependent cues will provide very little acoustic spatial information for the auditory system to accommodate to. We have recently completed an accommodation study where we first attempted to control for variations in the extent of spectral disruption produced by the mold and second, then focussed on the accommodation effects of training using sensory-motor feedback to source location.
The focus of the training regimes was to provide different levels of sensory and motor feedback each day of accommodation in addition to the subject's normal daily experiences. Given the theoretical modeling of the role of audio-motor feedback discussed above Aytekin et al. As before, localization testing and training was done in a darkened anechoic chamber. The first group received no performance feedback Control and just did three blocks of localization testing each day of accommodation; the second group received only visual feedback using a LED illuminated on the stimulus loudspeaker following each localization trial Visual ; the third group received visual and audio feedback where following each localization trial, the target loudspeaker pulsed at a rate inversely proportional to the nose-pointing error [Audio Visual Sensory Motor group AVSM ].
In an attempt to maximize the audio-motor feedback, subjects were encouraged to explore the space around the target by moving their heads and to minimize the pointing error using this audio feedback before registering their corrected response; the fourth group used the AVSM paradigm with the room lights turned on during training.
In contrast to previous studies, when compared to baseline, the acute effects of the molds were very similar for each group Figure 6 , Base cf. A0 , confirming that the standardization of the spectral perturbation had to a large extent been successful.kinun-houju.com/wp-content/kicyvurum/757.php
Virtual Auditory Space: Generation and Applications - Simon Carlile - Google книги
The difference in the feedback regimes can be seen most clearly in the front-back confusion rates by the tenth day of accommodation Figure 6 , top panel A While there was some improvement in the Control and Visual groups the most significant changes were for the groups receiving AVSM feedback. Similar improvement can also be seen with the elevation errors PAE although visual feedback alone was not significantly different to the AVSM feedback.
The allocentric frame of reference AVSM cf. AVSM-FOR did not seem to confer further advantage, consistent with the idea that spatial location is coded in body-centered coordinates that does not require an external reference frame Goossens and Van Opstal, Looking across the 10 days of accommodation it also appeared that AVSM feedback regimes produced a much quicker asymptote in performance at around 5—6 days data not shown.
Figure 6. The effects of training on accommodation to ear mold. Base: performance before accommodation with bare ears; A0: Performance on acute exposure to the mold; Acm performance following 10 days testing with feedback. Data from Carlile et al. Undoubtedly accommodation was occurring in the absence of any feedback-based training regime, presumably on the basis of the daily experience of the subject outside the laboratory, just as in the previous studies using ear molds.
By contrast, however, AVSM feedback, in particular, resulted in an increased rate of and greater extent of accommodation. Three other studies have employed similar forms of sensory-motor feedback in assisting listeners to accommodate to non-individualized HRTFs used in virtual auditory displays Zahorik et al. Interaction with the sound objects in the display was a key part of each study and some improvements in front-back confusion rates were generally found after relatively short periods of training Zahorik et al.
With a longer period of training 21 days of 2 h sessions improvements in both front-back confusion rates and elevation errors were reported Majdak et al. A very interesting outcome of these studies, when compared to those employing molds, is that the auditory system appears to be able to accommodate to a different set of cues even though it does not experience a consistent exposure to the new cues over the full period of accommodation. In the case of the virtual display studies, as soon as the training session is complete the listeners are then listening through their own ears. By contrast, the molds listeners are encouraged to keep them in their ears during all waking hours except when swimming or bathing.
Investigations of auditory adaptation to changes in the spectral inputs have highlighted a number of interesting and important aspects of auditory localization processing. It seems likely that localizing sounds in the real world involves a range of non-auditory inputs, which may also be co-opted in the process of accommodating to changes in the auditory cues. Firstly, despite the early focus on the visual system's involvement in the development of auditory representation, it appears that visual input is not necessary for auditory accommodation to cue changes in the mature animal.
There is a growing body of evidence that the motor state has an impact on the perception of auditory location. Again, the ecological problem of sound localization of even a single source is best characterized as a dynamic process involving the i transformation of the head-centered, acoustic cue coordinates to body-centered spatial coordinates and ii the disambiguation of source and self-motion.
On-line information regarding motor state is critical to such processing—whether this represents motor efference copy information as is the case for the visual system or proprioceptive feedback or a combination of the two is very much an open question. Regardless of the mechanism, motor state information has also been shown to be, theoretically, sufficient to establish a veridical representation of auditory spatial information.
In this light, the demonstrated capacity to recalibrate to acoustic cues that point outside the immediate visual field and the impact of audio-motor training regimes on accommodation should not be that surprising. The range of individual differences seen in previous spectral accommodation studies using ear molds could also reflect the audio-motor training opportunities available to the individual.
This of course raises the question of the capacity of such training regimes to promote, accelerate or complete accommodation to other forms spectral input changes including the application of hearing aids, changes to a hearing aid's processing or to the enhancement of the acoustic cues to location by the hearing aids. The role of attention and motivation in the perceptual learning of the altered spectral cues is likely to be a critical element in the success of any training regime see Amitay et al.
Although we have not been able to examine this literature in the course of this review there has also been much work in perceptual learning in the visual system e.
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A recent study of the HRTFs obtained through different hearing aid styles e. Behind the Ear demonstrated substantial spectral cue differences associated with different form factors Durin et al. Moving from one hearing aid style to another would be expected to be the equivalent at least of fitting ear molds as described above. Real time signal processing also provides the potential for enhancement of spectral or other cues to spatial location which could aid in localization Majdak et al.
Clearly these kinds of enhancements would require the auditory system to accommodate to substantial changes in the localization cues and efficient means of driving such accommodation would aid substantially in their utility. Of course, the most substantial accommodation required of the auditory system follows the fitting of a cochlear prosthesis, which requires many months or years of training. The challenge here is to broaden research and discover whether the audio-motor interactions underlying the accommodation to spatial cues can also be applied more broadly to spectrally-temporally complex signals such as speech.
No third party funds, other than the competitive grants provided by the Australian Research Council have been provided to support this research. The author would like to acknowledge Martin Burgess for comments and discussion on a previous version of the manuscript.
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Abel, S. The effect of aging on horizontal plane sound localization. Algazi, V.
Amitay, S. Discrimination learning induced by training with identical stimuli.
Aytekin, M. A sensorimotor approach to sound localization.