| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
The purpose of this study, entitled "Computational study on acoustic-image perception of object-shape from single-emission echo in bats", is to propose a new computational algorithm for representing an acoustic image of object-shape from an echo evoked by frequency-modulated ultrasonic sound and to examine it in the real world.
The acoustic image is an impulse response, known as a reflected-intensity distribution, which is composed of amplitude and phase spectra over a range of frequencies. However, bats detect only the amplitude spectrum due to the low-time resolution of their peripheral auditory system, and the frequency range of emission is restricted. Therefore, for representing the acoustic image, several constraints are needed to restore the reflected-intensity distribution from limited information.
The amplitude spectrum varies with the changes in the configuration of the reflected-intensity distribution, while the phase spectrum varies with the changes in its configuration and lo
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cation. As the constraints, the minimum phase condition and the continuity condition for the amplitude spectrum are introduced into the algorithm to restore the acoustic image from the single-emission echo. Simulated results indicated that the configuration can be extrapolated from the amplitude spectrum of the restricted frequency range, and the location can be estimated from the temporal changes of the amplitude spectra, and consequently the algorithm would restore the reflected-intensity distribution of an object regardless of its location or shape.
For applying the proposed algorithm to object-recognition in the real world, we designed an artificial external ear of the bat, i.e., a transfer-function modulator that is optimal for obtaining the orientation information, and constructed a system for echolocation and shape-recognition of objects in 3D space. Experimental results indicated that by using the artificial ear having the shape of truncated-horn, the system can determine location and surface-orientation of an object from the echo. Less
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