Specific outcomes from the project
Measurement of signal or impulse response
The characteristics of the signal have an important effect on the perceived width, and measurement of solely the impulse response does not reflect this.
The most common measurements of spatial impression that make use of the interaural cross-correlation coefficient are applied by analysing a binaural impulse response (equivalent to a click sounded at a stage position and captured at an audience position using a dummy head). However, it is apparent that impulsive signals (clicks or bangs) are dissimilar to the majority of the signals that make up music - especially classical music as may usually be performed in an auditorium.
A subjective experiment was conducted that demonstrated that the differences between wide-band impulsive signals and tonal more-continuous signals affect the perceived auditory source width of sounds. Firstly, it was apparent from the subjective results that the different musical signals that were used in the experiment were perceived to be different widths, even when reproduced through identical simulations of a concert hall. Secondly, it was apparent from the subjective results that IACC-based objective measurements made of the impulse responses did not match the subjective results, whereas measuring the stimuli themselves provided more accurate results.
This indicates that measurements that attempt to predict spatial impression should calculate the properties of signals that are similar to those that will be auditioned using the system or acoustical environment that is under test.
[Mason et al 2002