Spectral integration time of the auditory localisation system

For the elevation and front-versus-back hemifield of a sound source to be accurately determined, the sound must contain a broad range of frequencies.Experiment 1 of this study examined the spectral integration time of the auditory localisation system by measuring the accuracy with which frequency-modulated (FM) tones of modulation periods ranging from 0.5 to 200 ms can be localised. For each of the four participants, judgements of sound–source elevation and front–back hemifield were most accurate for a modulation period of 5 ms. Accuracy levels for the 5 ms modulation period approached those for a pink-noise stimulus. This suggests that the spectral integration time of the auditory localisation system is around 5 ms.Supporting evidence for this conclusion was sought in experiment 2, in which two participants localised noise stimuli that had magnitude spectra identical to those of 5 ms equivalent-rectangular-duration samples of the FM tones from experiment 1. For both participants, functions relating localisation error measures (i.e., elevation error and frequency of front–back confusion) to modulation period for spectrally matched noises were similar to those for FM tones.