Abstract
In this study, a new research method using psychoacoustic experiments and acoustic simulations is proposed for human echolocation research. A shape discrimination experiment was conducted for sighted people using pitch-converted virtual echoes from targets of dissimilar two-dimensional (2D) shapes. These echoes were simulated using a three-dimensional acoustic simulation based on a finite-difference time-domain method from Bossy, Talmat, and Laugier [(2004). J. Acoust. Soc. Am. 115, 2314-2324]. The experimental and simulation results suggest that the echo timbre and pitch determined based on the sound interference may be effective acoustic cues for 2D shape discrimination. The newly developed research method may lead to more efficient future studies of human echolocation.
Highlights
Bats are able to navigate spaces by actively producing ultrasounds and interpreting the echoes from objects for spatial and object recognition (Moss and Surlykke, 2010)
The amplitude waveforms and spectrograms of the original virtual echoes created by convolving the simulated echo impulse responses with the frequency modulated (FM) signal showed different patterns among the targets
The square and circle, which had the lowest discrimination performance in the psychoacoustic experiment (50.2 6 2.5%), showed similar patterns in the amplitude envelopes of the original virtual echoes (Fig. 2) and in the power spectra of the echo impulse responses for frequency ranges below 15 kHz [Fig. 3(A)]
Summary
Bats are able to navigate spaces by actively producing ultrasounds and interpreting the echoes from objects for spatial and object recognition (Moss and Surlykke, 2010). Sighted people can discriminate the wall thickness and materials of hollow cylinders and spheres by listening to pitch-converted echoes recorded using a typical bottlenose dolphin click within the ultrasonic range (DeLong et al, 2007). Pitch-converted ultrasonic broadband echoes enable sighted people to discriminate the edge contours and textures of three-dimensional (3D) shapes (Sumiya et al, 2019). These findings suggest that designing acoustic features of echolocation signals (e.g., frequency band and time-frequency structure) appropriately depending on the situation is effective for human echolocation. We aim to investigate human echolocation and propose effective and practical signal design and sensing strategies for human echolocation research
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