title: Cross-modulation interference with lateralization of mixed-modulated waveforms.
abstract: OBJECTIVE
  This study investigated the ability to use spatial information in mixed-modulated (MM) sounds containing concurrent frequency-modulated (FM) and amplitude-modulated (AM) sounds by exploring patterns of interference when different modulation types originated from different loci as may occur in a multisource acoustic field.
  
  
  METHODS
  Interaural delay thresholds were measured from 5 normal-hearing adults for an AM sound in the presence of interfering FM and vice versa as a function of interferer modulation rate. In addition, the effects of near versus remote interferer rates, and fixed versus randomized interferer interaural delay, were investigated.
  
  
  RESULTS
  AM interfered with lateralization of FM at all modulation rates. However, the FM interfered with AM lateralization only when the FM rate was higher than the AM rate. This rate asymmetry was surprising given the prevalence of low-frequency dominance in lateralization, but was predicted by a cross-correlation model of binaural interaction. Effects were similar for fixed and randomized interferer interaural delays.
  
  
  CONCLUSIONS
  The results suggest that in multisource environments, sources containing different modulation types significantly interfere with localization in complex ways that reveal interactions between modulation type and rate. These findings contribute to the understanding of auditory object formation and localization.
authors.affiliation: Department of Cognitive Sciences, University of California, Irvine, Irvine, CA 92692, USA.
authors.forename: I-Hui
authors.initials: IH
authors.lastname: Hsieh
authors.forename: Agavni
authors.initials: A
authors.lastname: Petrosyan
authors.forename: Oscar F
authors.initials: OF
authors.lastname: Gonçalves
authors.forename: Gregory
authors.initials: G
authors.lastname: Hickok
authors.forename: Kourosh
authors.initials: K
authors.lastname: Saberi
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000162:Acoustics; D001309:Auditory Threshold / Q000502:physiology; D004777:Environment; D006801:Humans; D008962:Models, Theoretical; D010470:Perceptual Masking / Q000502:physiology; D013017:Sound Localization / Q000502:physiology*