A method of estimating an individualized head-related transfer function and an individualized interaural time difference function of a particular person, comprises the steps of: a) obtaining a plurality of data sets comprising a left and a right audio sample from in-ear microphones, and orientation information from an orientation unit, measured in a test-arrangement where an acoustic test signal is rendered via a loudspeaker and the person is moving the head; b) extracting interaural time difference values and/or spectral values, and corresponding orientation values; c) estimating a direction of the loudspeaker relative to the head using a predefined quality criterion; d) estimating an orientation of the orientation unit relative to the head; e) estimating the individualized ITDF and the individualized HRTF. A computer program product may be provided for performing the method, and a data carrier may contain the computer program.