Effects of headphone calibration functions on subjective impressions of spatial sound

If the same sound pressure as when a listener were listening to the sound without headphones could be reproduced at the eardrum, the listener would perceive three-dimensional sound even when the sound is presented through headphones. Headphone calibration is therefore required to compensate for individual variations in the transfer function of a listener’s ear canal with and without headphones. From a practical point of view, a headphone calibration function applicable to many listeners would be attractive. We measured headphone calibration functions for 245 listeners, and from these data derived the mean calibration function. Its effects on the subjective impressions on spatial features of the reproduced sound were tested through listening tests. Participants compared various virtual three-dimensional sound signals generated by applying different calibration functions: mean calibration function and ones measured using different ears such as artificial ear (B&K 4153), head and torso simulator (B&K 4128), and listener’s own ear. Sound stimuli were presented in pairs, and rated by the participants in terms of diffuseness, externalization, and positional closeness between the perceived sound image and the actual loudspeaker corresponding to it. Statistical analyses of the results revealed that the mean headphone calibration function works well in terms of diffuseness and closeness.