Specific outcomes from the project
Optimum measurement window length
The optimum window length to use in the IACC measurements has been determined.
The results of IACC-based measurements of time-varying stimuli such as noise are strongly dependent on the window length used in the IACC calculations. In addition, the window length of the IACC calculation determines the rate of variation in either interaural time or level difference that is interpreted as movement or as decorrelation (and therefore width). For instance, a short window length will mean that only very rapid variations in interaural time or level difference are interpreted as decorrelation, and will infer that movement can be perceived up to a relatively fast rate of variation. On the other hand, a long window length will mean that relatively slow variations in interaural time or level difference are interpreted as decorrelation, and will infer that only very slow variations can be perceived as movement.
Previous research into the effect of different variation rates of the IACC on binaural masking level differences has indicated that the optimum window length is dependent on the subject and on the experiment type, with a range of 35 to 243 ms. Based on the rate of variations in interaural time and level difference that can be perceived as movement, a window length of 50 ms was estimated. This appears to be a reasonable estimation, and has been supported by the more detailed research into the temporal resolution of IACC perception discussed below.
[Mason et al 2003