Enhancing Externalization of Frontal Virtual Sound Sources in Binaural Synthesis via Level and Reflection Adjustment of Non-individualized BRIRs.
Kai-Lin Shen, Chao-Nan Wang
Two signal-processing tweaks to binaural room impulse responses—lowering frontal source volume to match lateral levels, and boosting early reflections—clearly made virtual sounds appear more 'outside the head' to listeners.
This is an audio-engineering finding, not a clinical intervention.
Key findings
1Scaling the binaural level of frontal BRIRs to match the 45° reference significantly improved externalization, with the largest gain at 0° (from 25.56 to 65.15 on a 0–100 scale).
2Amplifying the main reflections of the Scaling BRIR (Modified BRIR) was preferred over the Scaling BRIR in 83 of 100 comparisons at 15° and 84 of 100 at 0°, both p < .001.
3The consistent binaural level decrease from 0° to 45° was observed across four rooms of very different volumes (87.74 to 2032.28), suggesting the scaling factors are room-independent.
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What it does not show
Very small samples: 9 listeners in Experiment I and 10 in each Experiment II condition, all graduate students with self-reported normal hearing. Only pink noise was tested. The authors note that speech has an intermittent nature and restricted frequency range, so the method's effectiveness for speech is uncertain and may be more limited. The subjective listening test used only Room B, even though the scaling factors were derived from all four rooms. Generalizability to other room acoustics is inferred, not tested. No individualized BRIRs were used, and the study did not compare against them, so the absolute ceiling of externalization achievable is unknown. The study did not measure localization accuracy or distance perception directly; participants reported no noticeable degradation, but this was not formally tested.
Declared interests
The authors declared no financial support and no potential conflicts of interest.
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