HRTF (Head-Related Transfer Function) Spatial Audio and Pinna Diffraction: Edge Cases, Failure Modes, and Root-Cause Debugging

[Owen Phillips]

I’ve spent the last month stress-testing personalized HRTF profiles in competitive shooters, and I’m hitting frustrating edge cases that generic HRTF never gave me. When I run the in-ear calibration, front/back and up/down confusions drop significantly, but I’m still seeing failure modes around 6–8 kHz where the pinna diffraction peaks should be. My theory is that the concha and tragus reflections aren’t being captured accurately during the sweep, but I want to hear how you’re handling this. Are you using a measurement mic in the canal, or relying on the app’s camera-based ear-scan? And when you do get a clean personalized profile, how stable is it across different game engines—does Unreal’s reverb routing preserve the ITD cues better than the older spatializers?

The bigger problem I’m hitting is ILD collapse at low frequencies under 500 Hz. In dense firefights with stacked footsteps, the level differences wash out and I lose the elevation reading entirely. Is this a known limitation of the HRTF model itself, or am I hitting a sample-rate / buffer-latency issue on my interface? Also, how are you dealing with head-tracking drift corrupting the ITD baseline during long sessions, and do you apply any dynamic compensation when the user turns their head quickly?

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[Ryan Gray]

Great topic — I’ve spent way too many hours debugging spatial audio in competitive titles where mislocated footsteps literally costs rounds. The biggest edge case nobody talks about is the front/back confusion, and it almost always comes down to pinna diffraction cues. Generic HRTF libraries (Steam, Windows Sonic, even most console implementations) use average ear models, so the spectral notches above 6 kHz that your pinna creates to disambiguate elevation and front/back rarely match your actual ear geometry. If you’ve ever heard a footstep “above” you when it’s actually behind, that’s a HRTF mismatch, not a mix error. Custom HRTF capture (like the old Soneleics / head-scan approaches) dramatically reduces this, but it’s not widely adopted in-game. Also worth checking: the failure mode where spatializers collapse mono sources or reverberation tails onto

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