Wide-band underwater acoustic absorption based on locally resonant unit and interpenetrating network structure

The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic crystal （LRPC） exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters. Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of different samples were measured by the pulse tube. Measurement results show that the new material possesses excellent underwater acoustic effects in a wide frequency range.Moreover, in order to investigate impacts of locally resonant units,some defects are introduced into the sample. The experimental result and the theoretical calculation both show that locally resonant units being connected to a network structure play an important role in achieving a wide band strong acoustic absorption.

Adaptive grouped paired comparison:theory and selection of seeds

In the subjective sound quality evaluation based on paired comparison method, time cost grows with square of the number of samples, which makes the evaluation of large quantity of samples difficult. An adaptive grouped paired comparison （AGPC） design was proposed to greatly decrease time requirement and difficulties of subjective comparison test, and to avoid the reduction of the precision when improper reference samples were chosen in common grouped paired comparison by adapting the seeds. The mathematic theory and implementation method were given, including the experiential formulae. It was shown from computer simulations and the subjective sound quality evaluation that the results of the proposed AGPC method were in good agreement with the true merits of samples and those obtained from conventional paired comparison.