Specific outcomes from the project

Signal properties

The effect of source signal properties on IACC-based measurements


The division of source and environment related aspects of the signal based upon a single time point does not match perception well. More accurate results can be obtained by dividing the signal based upon perceptual streaming, separating segments perceived to be either a source or reverberation and measuring these individually.


A detailed investigation was undertaken to show that measurements made of wide-band transient impulsive signals give very different IACC values in a given acoustical environment compared to tonal more continuous signals. It was shown that this is due to two main factors. Firstly, the interactions between the direct sound and the reflections are dependent on the spectral properties of the signal. As impulsive signals are wide-band, this is very different to the majority of musical signals. Secondly, the duration of the signal affects the interaction between the direct sound and the reflections. Transient signals allow for very little interaction between the temporally separated direct sound and reflections, which means that no information can be gained about these interactions. The short duration of impulses is again very different to the majority of musical signals.

From this research it was concluded that the IACC of more continuous and tonal musical signals cannot be determined from measurements made of impulse responses, and that if the aim of the measurement is to predict the perceived effect of musical stimuli, more representative signals are required.


[Mason et al 2005b]