登录
 机构网站
  1. 首页
  2. 情报产品
  3. 快讯详情

《Fast computation of time-dependent acoustic fields》

  • 来源专题：水声领域信息监测
  • 发布时间：2016-11-25

  • A method for the fast evaluation of time-dependent acoustic fields from complex sources is presented. The technique is based on a fast integration method for the boundary integral arising in a Kirchhoff formulation and requires a small, and roughly constant, computation time to compute a transient signal, at the expense of a pre-processing stage. In the calculations in this paper, based on test cases for a single rotor, a counter-rotating open rotor, and a broadband volume source, it is found that transient field calculations require an order of magnitude less computational time for the field from an array of 16 384 sources, a computational advantage that increases with source number.

98浏览量
原文链接
相关报告

  • 《Impacts of environment-dependent acoustic propagation on passive acoustic monitoring of cetaceans》
    • 来源专题：水声领域信息监测
    • 发布时间：2016-11-21
    • Significant effort has been made over the last few decades to develop automated passive acoustic monitoring (PAM) systems capable of classifying cetaceans at the species level; however, these systems often require tuning when deployed in different environments. Anecdotal evidence suggests that this requirement to adjust a PAM system’s parameters is partially due to differences in the propagation characteristics. The environment-dependent propagation characteristics create variation in how a cetacean vocalization is distorted after it is emitted. If this is not accounted for, it could reduce the accuracy and precision of automated PAM systems. An aural classifier developed at Defence R&D Canada (DRDC) has successfully been used for inter-species discrimination of cetaceans. It achieves accurate results by using perceptual signal features that model the features employed by the human auditory system. To quantify the impacts of propagation on the perceptual features, an experiment was conducted in which bowhead and humpback whale vocalizations were transmitted over 1-20 km ranges during a two-day sea trial in the Gulf of Mexico. The experimental results will be presented and strategies will be discussed for training the classifier so that it is capable of operating in numerous acoustic environments with minimal adjustment of the classifier’s parameters.
    91浏览量
    原文链接

  • 《Inverse characterization of the frequency-dependent acoustic and elastic parameters of porous materials by surface-normal impedance method》
    • 来源专题：水声领域信息监测
    • 编译者：ioalib
    • 发布时间：2016-11-10
    • A method for characterizing the frequency-dependent acoustic and elastic parameters of porous materials is proposed and validated in the paper, based on the Biot theory. The parameters include the characteristic impedance, propagation coefficient (also denoted as complex wave number), and longitudinal modulus. The first two are the macroscopic acoustic properties of pore fluid, while the last one is the elastic property of frame. A system related to the three parameters is constructed through the normal surface impedance of three samples with different thickness, based on the transfer matrix theory. With the measured surface impedance and appropriate initial values, an iterative procedure based on the Newton–Raphson method is used to solve the system. The three parameters are identified simultaneously, and then validated by two experimental methods, respectively, i.e., a modified two cavity method for the acoustic parameters and a quasi-static mechanical method for the elastic parameter. The parameters identified from the proposed method are consistent with the results of the two methods except for the imaginary part of the longitudinal modulus. It is shown that the proposed method would have a better performance if the discrepancy of frame displacements among different samples is moderate, corresponding to a reasonable selection of the thickness.
    143浏览量
    原文链接