EXPERIMENTAL INVESTIGATION ON THE DESIGN OF BIONIC COMPOSITE MULTILAYER SOUND-ABSORPTIVE STRUCTURE MIMICKING LONG-EARED OWL

摘要

A new 4-unit composite sound-absorptive structure composed of fibers, membrane, cavities and porous aluminium foam is designed by mimicking the sound absorptive characteristics of the feathers, skin and subcutaneous tissue of long-eared owl. The sound absorption coefficients of the designed bionic composite structures are tested in an impedance tube with the standard transfer function method, complying with the Chinese national standard GBT-18696.2-2002, which is equivalent to the ISO 10534-2:1998. The result shows that compared with the traditional sound-absorptive structure, the designed bionic structure demonstrates effectively improved sound absorption performance in the medium frequency range from 400 Hz to 1.6 kHz. Particularly, the sound absorption coefficient of the bionic composite structure covered by cotton and wool can approach one at an extremely fast rate starting from 400 Hz. At the same time, weight and cost comparison shows that the bionic sound-absorptive structures have greater advantages than the traditional aluminium foam. Hence it can be concluded that the proposed new structure has great potential for applications in the field of audio stealth.