An audio personalisation method for a user includes: testing the user with an audio test, the audio test comprising: moving a portable device, comprising a position tracking mechanism and a speaker, to a plurality of predetermined test positions relative to the user's head; when within a threshold distance of a predetermined test position, playing a test sound through the speaker of the portable device; and detecting the test sound using a microphone proximate to each of the user's ears, and associating resulting measurement data with the predetermined test position, where the resulting measurement data derived from the detected test sounds is characteristic of the user's head morphology; for a corpus of reference individuals for whom respective HRTFs have been generated, comparing the measurement data from the user's audio test or a head-related transfer function ‘HRTF’ derived from this measurement data with corresponding measurement data of some or all respective reference individuals in the corpus or HRTFs of some or all respective reference individuals in the corpus; identifying a reference individual whose measurement data or HRTF best matches the measurement data or HRTF from the user's audio test; and using the HRTF of the identified reference individual for the user.