The Echobot: An automated system for stimulus presentation in studies of human echolocation

Abstract

Echolocation is the detection and localization of objects by listening to the sounds they reflect. Early studies of human echolocation used real objects that the experimental leader positioned manually before each experimental trial. The advantage of this procedure is the use of realistic stimuli; the disadvantage is that manually shifting stimuli between trials is very time consuming making it difficult to use psychophysical methods based on the presentation of hundreds of stimuli. The present study tested a new automated system for stimulus presentation, the Echobot, that overcomes this disadvantage. We tested 15 sighted participants with no prior experience of echolocation on their ability to detect the reflection of a loudspeaker-generated click from a 50 cm circular aluminum disk. The results showed that most participants were able to detect the sound reflections. Performance varied considerably, however, with mean individual thresholds of detection ranging from 1 to 3.2 m distance from the disk. Three participants in the loudspeaker experiment also tested using self-generated vocalization. One participant performed better using vocalization and one much worse than in the loudspeaker experiment, illustrating that performance in echolocation experiments using vocalizations not only measures the ability to detect sound reflections, but also the ability to produce efficient echolocation signals. Overall, the present experiments show that the Echobot may be a useful tool in research on human echolocation.

A framework to account for the effects of visual loss on human auditory abilities.

“…Within the blind population, those who echolocate often have real-life advantages, including higher salary and higher mobility in unfamiliar places, than those who are not echolocators (Thaler, 2013). Successful echolocation depends on the ability to produce appropriate signals, such as tongue clicks, and to detect and discriminate the sound reflections (Tirado, Lundén, & Nilsson, 2019). Although both sighted and blind people are able to echolocate, blind people display enhanced skills for several aspects of echolocation, including object detection (Kolarik, Scarfe, Moore, & Pardhan, 2017c;Rice, 1969) and localization (Rice, 1969;Schenkman & Nilsson, 2010, 2011, discrimination of the spatial positions of two disks (Teng & Whitney, 2011), discrimination of object material or texture (but not density, Hausfeld, Power, Gorta, & Harris, 1982;Kellogg, 1962), judgment of size and distance (Kellogg, 1962), and shape (Hausfeld, et al, 1982), and when using sound to navigate around obstacles (Kolarik, et al, 2017c) or to walk in a straight line parallel to a wall (Strelow & Brabyn, 1982).…”

Comparing Echo-Detection and Echo-Localization in Sighted Individuals

“…We used naı¨ve participants and therefore used a prerecorded echolocation signal, not to confuse the ability to perceive sound reflections from the ability to produce efficient echolocation signals (cf. Tirado et al, 2019). This limits the generalizability of the results, as it is possible that expert echolocators using self-generated echolocation signals would show a different echo-detection versus echo-localization pattern.…”

“…The Echobot consists of platforms that can be programmed to move across a 4 m-long rail and to horizontally rotate vertical disks of different sizes and materials. In the present experiment, it is a circular aluminum disk 50 cm in diameter and 0.4 cm thick (see Tirado et al, 2019 for further details on the Echobot). The Echobot allows for a more rigorous and time-efficient application of psychophysical methods than previous nonautomated paradigms.…”

“…The Echobot was placed in a soundproof listening laboratory with a low background level (<20 dB [A]) and short reverberation time (<0.1 between 0.25 and 8 kHz). The floor area was 5.3 Â 4.0 m 2 with a ceiling height of 3 m (see Tirado et al, 2019 for more details on the acoustics of the masking noise and the soundproof laboratory). There was a loudspeaker rig intended for other types of experiments present in the room, but the rig was covered with soft dampening material to eliminate reflections and resonances (the rig is not visible in the photos of Figures 1 and 2).…”

“…In the present experiment, we tested 10 naı¨ve-sighted participants on their echo-detection and echo-localization abilities. An automated method, referred to as the Echobot, was used to allow rigorous psychophysical testing with real sounds, distances, and reflecting objects (Tirado et al, 2019). The purpose was to explore at what distances naı¨ve listeners would be able to detect and localize sound reflections.…”