Auditory localisation of low-frequency sound sources

It is generally thought that humans cannot detect the direction of sound in the very low-frequency spectrum, although some studies suggest that the sense of direction also exists at the lowest audible frequencies. In the current work, a 2AFC localisation experiment is conducted with 18 participants, where the listener must detect a change in the direction of pure tones and octave band filtered pink noise bursts in the frequency range of 31.5 to 100 Hz. The angular separations between the low-frequency sound events utilised in the test are 10, 20, 25, 35 and 45 degrees in the left azimuth plane. The results agree with those studies showing that humans can localise even the lowest audible frequencies. Changes in direction as small as 10 degrees can be reliably detected for pink noise bursts from 31.5 Hz and for pure tones from 63.5 Hz. The psychoacoustic experiment was conducted in an anechoic room with minor room resonances which caused a significant change in the directional judgement for the affected frequencies, demonstrating how strongly room resonances can interact with directional hearing in the low-frequency spectrum.