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Human Echolocators adjust loudness and number of clicks for detection of reflectors at various azimuth angles.

Thaler, Lore and De Vos, Henrikus and Kish, Daniel and Antoniou, Michail and Baker, Chris and Hornikx, Maarten (2018) 'Human Echolocators adjust loudness and number of clicks for detection of reflectors at various azimuth angles.', Proceedings of the Royal Society series B : biological sciences., 285 (1873). p. 20172735.

Abstract

In bats it has been shown that they adjust their emissions to situational demands. Here we report similar findings for human echolocation. We asked eight blind expert echolocators to detect reflectors positioned at various azimuth angles. The same 17.5 cm diameter circular reflector placed at 100 cm distance at 08, 458 or 908 with respect to straight ahead was detected with 100% accuracy, but performance dropped to approximately 80% when it was placed at 1358 (i.e. somewhat behind) and to chance levels (50%) when placed at 1808 (i.e. right behind). This can be explained based on poorer target ensonification owing to the beam pattern of human mouth clicks. Importantly, analyses of sound recordings show that echolocators increased loudness and numbers of clicks for reflectors at farther angles. Echolocators were able to reliably detect reflectors when level differences between echo and emission were as low as 227 dB, which is much lower than expected based on previous work. Increasing intensity and numbers of clicks improves signal-to-noise ratio and in this way compensates for weaker target reflections. Our results are, to our knowledge, the first to show that human echolocation experts adjust their emissions to improve sensory sampling. An implication from our findings is that human echolocators accumulate information from multiple samples.

Item Type:Article
Full text:(AM) Accepted Manuscript
First Live Deposit - 12 February 2018
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1098/rspb.2017.2735
Publisher statement:© 2018 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
Record Created:12 Feb 2018 09:43
Last Modified:01 Mar 2018 12:19

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