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|Title: ||Absolute auditory object localization|
|Authors: ||Shotter, Emily|
|Issue Date: ||1997|
|Publisher: ||© Emily Shotter|
|Abstract: ||This thesis concerns the potential use of auditory virtual reality (A VR) in safety-critical
situations. Localization accuracy is essential in many VR situations, such as simulated
cockpits, where vision is fully occupied and targets must be signified acoustically.
However, the errors reported for localizing 3D sounds varies considerably in the
literature and some (e.g. Wightman & Kistler, 1989; Wenzel et aI, 1993) report fairly
large errors. This thesis consists of an evaluation of the use of acoustic cues to indicate
the location of certain targets.
A Knowles Electronic Manikin for Acoustic Research (KEMAR) was used to examine
the effects of individualized pinnae on localization accuracy. The results showed that
using our own pinnae over foreign pinnae provides little or no benefit. More
surprisingly, substantial errors were observed in this study. This initial result drove the
fundamental investigation into the large angle errors.
The method of eliciting subject responses was investigated. The findings established
response method as an important methodological feature in localization experiments
from the significant effect it has on the results. Error values can be halved when using
a categorical method, compared to an unguided (non-categorical) method, possibly
because it constrains the subjects' response options. A further possible constraint on
subject responses is the effect of memory in absolute judgement tasks. If the memory
of one sound impinges on subsequent sounds then the subject's judgement is
constrained and the measurement of error may be contaminated. This effect was
studied by introducing variable delays that should affect memory .(0 a different extent.
No obvious differences in accuracy were noted. This rules out 'interstimulus interval'
as a cause for the variability of reported angle errors.
Stimulus types were varied in an effort to maximise acuity. Although broadband
sounds are purported to give the smallest errors (e.g. Stevens & Newman, 1936;
Sandel et aI, 1955), this investigation offered a unique comparison of long and shortduration
broadband and complex sounds. But consistently high angle errors forced the
inclusions of non-acoustic cues such as vision and head movements, which decreased
the error to between 0° and 7°.
The implicatioos for VR in light of the importance of vision (demonstrated by this
work), are that it is 'not advisable to implement an auditory cueing system that may
conflict or fail to be guided by vision. Where high levels of accuracy are required, as is
paramount in safety-criticalsituations, auditory localizatioo is not sufficient as a sole
cue to target location.
Scientific conclusion: The acoustic cues alone (independent of context) cannot support
accurate auditory localization.
Applications conclusion: It is not advisable to implement an auditory cueing system that
is not guided by vision.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Design School)|
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