1. Localising multiple sounds

2. Phenomenology Different sounds localised appropriately The whole of a sound is localised appropriately …even when cues mangled by reverberation, so information in any one frequency region is unreliable.

3. Grouping Which frequency components belong to which sound? Low-level cues –Onset time –Harmonicity Schemata

4. Phase Ambiguity 500 Hz: period = 2ms R leads by 1.5 msL leads by 0.5 ms LLR cross-correlation peaks at +0.5ms and -1.5ms auditory system weighted toone closest to zero 500-Hz pure tone leading in Right ear by 1.5 ms Heard on Left side

5. Disambiguating phase- ambiguity Narrowband noise at 500 Hz with ITD of 1.5 ms (3/4 cycle) heard at lagging side. Increasing noise bandwidth changes location to the leading side. Explained by across-frequency consistency of ITD. (Jeffress, Trahiotis & Stern)

6. Resolving phase ambiguity 500 Hz: period = 2ms L lags by 1.5 msor L leads by 0.5 ms ? -2.5 200 800 600 400 -0.51.53.5 Delay of cross-correlator ms Frequency of auditory filter Hz Cross-correlation peaks for noise delayed in one ear by 1.5 ms 300 Hz: period = 3.3ms R RLLR Actual delay Left ear actually lags by 1.5 ms L lags by 1.5 msor L leads by 1.8 ms ? R

7. Segregation by onset-time 200 400 600 800 Frequency (Hz) Duration (ms) 0400 Duration (ms) 080400 SynchronousAsynchronous ITD: ± 1.5 ms (3/4 cycle at 500 Hz)

8. Segregated tone changes location -20 0 20 0 4080 Onset Asynchrony (ms) Pointer IID (dB) Pure Complex RL

9. Segregation by mistuning 200 400 600 800 Frequency (Hz) Duration (ms) 0400 Duration (ms) 080400 In tuneMistuned

10. Mistuned tone changes location

11. Interim Summary ITD ineffective for simultaneous segregation Integration of ITD across frequency influenced by grouping cues Question: Can attention be directed on the basis of ITD to grouped objects?