Monaural Adaptive Mechanisms in Human Sound Localization

12 Monaural and binaural listeners 12 Apparatus 14 Auditory stimuli 14 Paradigms 15 Data analysis 15 2.3 Results 18 The influence of intensity on monaural sound-source azimuth localization 18 The influence of spectral cues on monaural sound-source azimuth localization 22 Monaural sound-elevation localization 25 Training to localize azimuth monaurally 27 2.4 Discussion 28 Acknowledgements 31 Chapter III 33 Sound Localization under Perturbed Binaural Hearing 3.1 Introduction 34 3.2 Methods 35 Participants 35 Apparatus 35 Auditory stimuli 36 Plugs 37 ii Measurement of audiograms 37 Paradigms 37 Hearing Conditions 37 Data analysis 37 3.3 Results 39 Acute effects of a unilateral plug 39 Influence of sound intensity and source azimuth on azimuth localization 40 Influence of intensity and azimuth on elevation localization 45 Weighting of cues 48 3.4 Discussion 50 Spectral cues for azimuth 50 Azimuth cues for elevation 51 Monaural Listening 51 Integration of acoustic cues 52 Neural mechanisms 52 Acknowledgements 53 Participants 58 Apparatus 58 Auditory stimuli 58 Molds 59 Measurements of directional transfer functions 60 DTFs and their correlations 60 DTF similarity index 60 Paradigms 61 Hearing conditions 61 Front-back reversals and confusions 62 Data analysis 62 4.3 Results 63 Acute effects of a unilateral spectral perturbation 63 Conflicting spectral shape cues 67 Adaptation to a unilateral mold 68 Front-back reversals 72 Test of the adaptation models 72 4.4 Discussion 75 Summary 75 Comparison to other studies 75 Learning behavior 75 Potential mechanisms 76 Other factors 76 Calibration 77 iii Outlook and applications 77 Acknowledgements 77 Chapter V 79 Auditory-Visual Interactions Subserving Goal-Directed Saccades in a Complex Scene 5.1 Introduction 80 5.2 Methods 82 Subjects 82 Apparatus 82 Stimulus Generation 82 Paradigms 83 Data analysis 84 5.3 ResultS 86 Properties of unimodal V-saccades and A-saccades 86 Properties of AV-saccades (no temporal asynchronies) 89 AV interactions as a function of stimulus timing 93 AV-control experiment 97 5.4 Discussion 97 Consideration of mechanisms other than neural integration 98 Rules for multisensory integration of bimodal signals and comparison to previous work 100 Conceptual model of auditory-visual interactions in a complex scene 101 Conclusions 103 Acknowledgements 103