Echolocation vs. echo suppression: influence of the precedence effect on the human-sonar localization of reflective surfaces

Abstract

Event Abstract Back to Event Echolocation vs. echo suppression: influence of the precedence effect on the human-sonar localization of reflective surfaces Ludwig Wallmeier1*, Nikodemus Geßele1 and Lutz Wiegrebe1 1 Ludwig-Maximilians-Universität München, Graduate School of Systemic Neurosciences, Germany Echolocation is an effective perception-action ability of humans, especially used by blind people. However, the precedence effect predicts a conflict of echo analysis and echo suppression: when localizing sound sources, the human auditory system suppresses spatial information of echoes, but just this information underlies effective echolocation. A common approach to investigate the precedence effect is the arrangement of two sound sources that present a direct sound (lead) and a delayed copy (lag). Several experiments on lag-discrimination suppression have quantified the deterioration of spatial information of the lag produced by the lead. This study investigates the interaction of echolocation and precedence effect in terms of discrimination suppression. Sighted subjects performed two versions of an azimuth-discrimination experiment in virtual acoustic space: In the ‘listening’ version, subjects had to discriminate between positions of a single sound source, the leading, or the lagging of two sources, respectively. In the ‘echolocation’ version, the sound sources were replaced by sound reflectors. Here, subjects evaluated the echoes generated in real time from self-produced vocalizations and thereby discriminated between positions of a single reflector, the leading, or the lagging of two reflectors, respectively. Our results show that sighted subjects can be trained to discriminate reflective surfaces by echolocation with accuracy comparable to sound source localization. In the listening version, the presence of a lagging source impaired lead-discrimination only slightly by a factor of 1.6, while a leading source impaired lag-discrimination considerably by a factor of 8.8. The asymmetry between lead- and lag-discrimination shows a strong influence of the precedence effect, which facilitates localization of the lead at the expense of the lag. In the echolocation version, however, this asymmetry was significantly weaker: lead and lag discrimination deteriorated by a factor of 4.8 and 6.2, respectively. These data indicate that the precedence effect is weakened in an echolocation context. Acknowledgements This study was supported by 'Studienstiftung des deutschen Volkes' and 'Graduate School of Systemic Neurosciences'.