Specific outcomes from the project

Frequency dependent properties

Width of diotic stimuli dependent on frequency


The frequency dependence of the perceived width of diotic stimuli (signals identical at both ears) has been determined, and an equation derived to model this in the measurement.


Previous research has indicated that the perceived width of narrow-band stimuli with identical IACC values is dependent on the centre frequency of the stimuli, even when they are as simple as single sine tones. However, a method to compensate for this had not been derived.

A series of experiments were conducted to investigate this further. An experiment was conducted to investigate the perceived width of narrow-band diotic stimuli (i.e. with an IACC of 1). As the perceived auditory source width is inversely related to the IACC, this provides the narrowest perceived width at each frequency that can serve as a baseline against which changes due to variations in the correlation can be measured. It was found that low frequency stimuli are perceived to be widest, with a gradual decrease in the width as the frequency rises to approximately 1.5 kHz. In the range from approximately 1.5 kHz to approximately 3.5 kHz, the stimuli are perceived to be relatively narrow, and the width then increases with increasing frequency beyond this. A method for compensating for this was devived that was added to the measurement model.


[Mason et al 2005a]