Development of a Perceptual Model for the Trade-off Between Interaural Time and Level Differences for the Prediction of Auditory Image Position

In the current study, a simplistic and linear ITD-ILD trade-off model based on subjective
data has been proposed to allow for various combinations of interaural time and level
differences (ITD and ILD) for positioning auditory images at azimuth angles up to 60°.
This can also be used to predict the azimuths of auditory images from input ILD and ITD.
Independent ILD and ITD values used to generate the model were obtained through a
lateral pointer task using a novel method which utilises HRIRs for defining azimuth
position. From analysing the model, it was found that combination values were smaller
compared to natural combinations extracted from HRTF in localisation. This was also
apparent in a virtual localisation experiment where subjects used a HRIR pointer to
report the azimuth of auditory image, laterally displaced by various ILD-ITD
combinations from the model. It was found that the perceived angles were persistently
narrower than their target angles. This underestimation was more significant for wider
target angles above 45° and for ILD/ITD combination ratios with a larger weighting of
ILD.