The principle of out-of-head sound image localization technology is the correction of the sound stimulus at the eardrum in the free sound field and that at the eardrum of the headphone listener to equalize them. A correction filter is designed assuming that the pressure division ratio (PDR) is unity. However, it is impossible to strictly achieve a PDR of one, which can result in a timbre change of the reproduced sound. In this study, to reproduce the original sound field more faithfully, we used open-ear-canal microphones instead of the conventionally used blocked-ear-canal microphones and evaluated sound reproducibility from the viewpoint of PDR. It was found that the PDR was closer to one when recording with the ear canal open than with the ear canal blocked. In addition, the angular dependence due to the presentation direction of the sound source was reduced. The dependence on the position of the microphone placed in the ear canal was low. From the viewpoint of sound field reproducibility at the position of the eardrum, the validity of using an open-ear canal microphone was confirmed by experiments.
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