1. Learning the cues associated with non-individualised HRTFs John Worley and Jonas Braasch Binaural and Spatial Hearing Group

2. Head-Related Transfer Functions

3. Binaural and Spatial Hearing Group Individual Differences in HRTFs  Highly idiosyncratic.  Differences in HRTF magnitude due to differences in the size and shape of pinnae.  Inter-subject differences in level as much as 28 dB (Wightman & Kistler, ‘89a).

4. Binaural and Spatial Hearing Group Using Non-Individualised HRTFs Binaural cues cue multiple locations. Cones of confusion lead to reversal errors. Non-individualised HRTFs result in a 3-fold increase in reversals over individualised HRTFs.

5. Binaural and Spatial Hearing Group Learning non-individualised HRTFs Listeners adapt to long-term pinna modifications (Hofman et al, ’98). Scaling non-individualised HRTFs improves localisation (Middlebrooks, ‘99). Localisation is unaffected by smoothing HRTFs (Kulkarni & Colburn, ’98). Visual system calibrates auditory input Early-blind listeners (Zwiers & Van Opstal, ’01). Compressed visual space compresses auditory space (Zwiers,’03).

6. Binaural and Spatial Hearing Group Methodology Headphone-based azimuth localisation of scrambled noise. HRTFs from prototype Neumann KU80 (pinna molded from average pinna). 12 possible locations, surrounding the listener. Instructed to respond to auditory event. Responses recorded via GELP method (Gilkey et al 1995). Test auditory localisation over time: Day 1 = Auditory alone Day 1 to 9 = Auditory location cued by visual stimuli Day 10 = Auditory alone

7. Binaural and Spatial Hearing Group Methodology - Testing 330° X

8. Binaural and Spatial Hearing Group Methodology - Training 210°

9. Rear Results

10. Rear Results Perfect localisation

11. Rear Results Rear Results Front-to-back mislocalisation

12. Results Day 1- Testing Responses clustered in the rear hemisphere.

13. Results Training Type – I (2 listeners) Type - II (3 listeners) Response bias

14. Results All Days- Testing Majority of front-to-back reversals. No reduction in reversals as a function of time.

15. Results All Days- Testing Type - I Type - II Type – I = No reversal predisposition. Type- II = Majority of front-to-back reversals. Response bias significantly determines reversal type

16. Conclusions Listeners display a response bias. Response bias determines reversal type. Overall, Non-sig. reduction in reversals over training period. Why?, Difference between passive -v- dynamic listening. Individualised head -v- dummy head.