You’re absolutely right that the most effective simulation would use a custom HRTF for each person, as the shape of the head, shoulders, pinnae of the ear etc e

You’re absolutely right that the most effective simulation would use a custom HRTF for each person, as the shape of the head, shoulders, pinnae of the ear etc etc. all play some part... There are some headphones that attempt to go some way towards this by taking pictures of/otherwise ‘scanning’ the users ear (eg. https://electronics.sony.com/360-reality-audio https://electronics.sony.com/360-reality-audio https://mysofa.audio/ https://mysofa.audio/ …paper on the subject: https://www.aes.org/e-lib/browse.cfm?elib=19855 https://www.aes.org/e-lib/browse.cfm?elib=19855 …interestingly, for Apple’s future plans perhaps, ear canal used for biometric validation: https://dl.acm.org/doi/10.1145/3351239 https://dl.acm.org/doi/10.1145/3351239 ) The strongest ‘cue’ is probably the ‘interaural time delay’, which is easy enough to fake, but as you say, without fixed sources (imagine the calibration/setup of a VR headset) and subsequently taking into account that people actually turn/tilt their heads to better appreciate the direction a sound is coming from, as apparently Apple does relative to the device the tracks are playing from: https://appleinsider.com/articles/21/05/18/apples-spatial-audio-and-dolby-atmos-explained https://appleinsider.com/articles/21/05/18/apples-spatial-au... (in order to take best advantage of what you experienced where we can better locate left/right than forward/back...), the efficacy is reduced. Generally we are also much better at localizing sounds in the lateral plane than the vertical one (…evolutionarily perhaps this was more important in order to avoid being eaten by sabre-toothed tigers or something? :) There are other cues deriving from ‘head-shadow’ (somewhat like an eq.), reflection from shoulders and even reflections from the acoustic environment and so on that are subtler/more complicated… Traditionally dummy heads with anatomically ‘average’ characteristics and binaural microphones in the ‘ears’ have been used to make binaural recordings, but if you were to venture out with binaural microphones in your ears and then later play back the recordings the effect can be startlingly effective… [as an aside, when I posted the above comment in this thread a couple of days ago when it was first on HN, the title of the post was ‘Spatial Audio is a Scam’ :) ]