Specific outcomes from the project
Display and interpretation factors
Combination of location and width detection
The relationship between the measured source width and the measured location in terms of the interaural time difference has been determined. This allows measurements of perceived location and width to be combined for a more complete spatial analysis.
It is logical to expect that the lateral position of individual frequency components can affect the overall perceived auditory source or environment width. For instance, if a low frequency component is perceived to be towards the left and a high frequency component of a similar width is perceived to be towards the right, the overall width can be interpreted to be from the left hand side of the low frequency component to the right hand side of the high frequency component. If the lateral position of each of these components was not taken into account, then the overall measured width would simply be the wider of the two individual scene components.
In order to take the lateral position into account, a measure of the perceived position needs to be introduced to the model, and the results need to be converted to a common scale. There are a number of binaural hearing models that predict the perceived location of the sound that can be used. A series of experiments were undertaken to be able to convert the predictions of the perceived auditory source width to a location-based scale. This involved subjects adjusting the ITD of marker stimuli to denote the edge positions and widths of a range of stimuli. An equation to map the IACC-based width measurements to a scale of ITD was derived and implemented in the hearing model.
[Mason et al 2004c