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Durham University



Publication details for Dr Lore Thaler

Thaler, Lore, De Vos, Henrikus, Kish, Daniel, Antoniou, Michail, Baker, Chris & Hornikx, Maarten (2018). Human Echolocators adjust loudness and number of clicks for detection of reflectors at various azimuth angles. Proceedings of the Royal Society B: Biological Sciences 285(173): 20172735.

Author(s) from Durham


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.

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