厅堂音质的听觉化模拟技术

厅堂音质的听觉化模拟技术是计算机技术、室内声学、电声技术相结合的双耳听觉化模拟技术，是新一代的厅堂音质ＣＡＤ技术的关键。同时听觉化模拟技术也为未来新的立体声制式的出现提供了可能性，这对未来的数字立体声广播、多媒体广播都可能产生巨大的潜在影响。本文对此项技术的原理、声场模拟、听演化实现过程、软件研究及应用前景等作了简要的介绍。     

模糊聚类在城市环境噪声区划中的应用

通过对城市声学环境定量区划方法的研究,提出使用模糊聚类模型进行区划,该方法简单,误差小,具有较强的实用价值.     

Frequency domain analysis of acoustic wave propagation in heterogeneous media considering iterative coupling procedures between the method of fundamental solutions and Kansa's method

Acoustic wave propagation in heterogeneous media is a topic of significant interest in many areas of science and engineering, including aeroacoustics and sound propagation in oceans. In the present work, numerical frequency domain models based on the joint use of the method of fundamental solutions and of the radial basis function collocation method (also known as Kansa's method) are discussed. In this context, the method of fundamental solutions is used to model the homogeneous part of the propagation domain, while Kansa's method is employed to model the presence of heterogeneities. The coupling between the two parts of the propagation domain is performed iteratively, allowing independent spatial discretization between the different subdomains of the model (i.e. matching collocation points at common surfaces are not necessary). Additionally, an optimised algorithm, based on the use of a varying relaxation parameter, is employed to speed up and/or to ensure the convergence of the iterative coupling process. At the end of the paper, numerical results illustrate the applicability and potentialities of the proposed formulations. Copyright © 2011 John Wiley & Sons, Ltd.     

Categorization of seismic sources by auditory display: A blind test

Recordings of the Earth's surface oscillation as a function of time (seismograms) can be sonified by compressing time so that most of the signal's frequency spectrum falls in the audible range. The pattern-recognition capabilities of the human auditory system can then be applied to the auditory analysis of seismic data. In this experiment, we sonify a set of seismograms associated with a magnitude-5.6 Oklahoma earthquake recorded at 17 broadband stations within a radius of ∼300 km from the epicenter, and a group of volunteers listen to our sonified seismic data set via headphones. Most of the subjects have never heard a sonified seismogram before. Given the lack of studies on this subject, we prefer to make no preliminary hypotheses on the categorization criteria employed by the listeners: we follow the “free categorization” approach, asking listeners to simply group sounds that they perceive as “similar.” We find that listeners tend to group together sonified seismograms sharing one or more underlying physical parameters, including source–receiver distance, source–receiver azimuth, and, possibly, crustal structure between source and receiver and/or at the receiver. This suggests that, if trained to do so, human listeners can recognize subtle features in sonified seismic signals. It remains to be determined whether auditory analysis can complement or lead to improvements upon the standard visual and computational approaches in specific tasks of geophysical interest.     

Local fault detection in helical gears via vibration and acoustic signals using EMD based statistical parameter analysis

Gear is a vital transmission element, finding numerous applications in small, medium and large machinery. Excessive loads, speeds and improper operating conditions may cause defects on their bearing surfaces, thereby triggering abnormal vibrations in whole machine structures. This paper describes the implementation of empirical mode decomposition (EMD) method for monitoring simulated faults using vibration and acoustic signals in a two stage helical gearbox. By using EMD method, a complicated signal can be decomposed into a number of intrinsic mode functions (IMF) based on the local characteristic time scale of the signal. Vibration and acoustic signals are decomposed to extract higher order statistical parameters. Results demonstrate the effectiveness of EMD based statistical parameters to diagnose severity of local faults on helical gear tooth. Kurtosis values from EMD and that obtained from vibration and acoustic signals are compared to demonstrate the superiority of EMD based technique.     

穿孔管消声器声学性能三维时域计算及分析

将三维时域计算流体动力学(Computational fluid dynamics,CFD)法应用于计算有流情况下穿孔管消声器的声学性能。在消声器进口处施加脉冲信号与不施加任何信号的两种情况下,通过非定常计算分别得到消声器上下游监视点的时域压力值。同一监视点两次计算结果之差就是脉冲信号及其反射信号。使用快速傅里叶变换将时域声压信号转换到频域,计算出消声器的传递损失。对于直通穿孔管消声器和横流穿孔管消声器,使用三维时域CFD法计算传递损失,并与试验测量结果和频域法计算结果进行比较,以验证三维时域CFD法预测穿孔管消声器声衰减性能的准确性。分析气流速度和温度对横流穿孔管消声器传递损失的影响。结果表明,随着气流速度的增加,传递损失曲线向低频方向移动,多数频率处的传递损失有所增加;随着介质温度的升高,传递损失曲线向高频方向移动。     

Enhancing nearfield acoustic holography using wavelet transform

When there are low signal to noise relationships or low coherences between measured pressure and a reference sensor, a pressure field measured and estimated by NAH (Nearfield Acoustic Holography) becomes noisy on the hologram and source planes. This paper proposes a method to obtain the high coherent de-noised pressure signals from low coherent noisy ones by combining a wavelet algorithm with NAH. The proposed method obtains the de-noised field from acoustic fields on a noise source plane reconstructed through backward propagation of NAH. Thus this method does not need high coherent pressure signals on the hologram surface while the conventional nearfield acoustic holography requires high-coherent signals. The proposed method was verified by numerical simulation using noisy signals, composed of original signals and imposed noises distributed on the hologram surface.     

基于声信号三维谱分析的转子故障特征提取的实验研究

对转子的一些典型故障（不平衡、松动、碰磨、不对中以及突加不平衡）进行试验模拟,对故障发生过程中的声信号采用声望话筒和十六通道索尼磁带记录仪进行采集的基础上,分析转子故障声信号的三维谱特性,提取和总结出由故障造成的声信号突变和对应的声谱特征。分析结果表明,采用声信号对转子的一些故障进行诊断是可行的。     

Assessing the influence of inflow turbulence on noise and performance of a tidal turbine using large eddy simulations

Large eddy simulations of a model scale tidal turbine encountering inflow turbulence have been performed. This has allowed both unsteady blade loading and hydrodynamic noise radiation to be predicted. The study is motivated by the need to assess environmental impact of tidal devices, in terms of their acoustic impact on marine species.Inflow turbulence was accounted for using a synthetic turbulence generator, with statistics chosen to represent the gross features of a typical tidal flow. The turbine is resolved in a fully unsteady manner using a sliding interface technique within the OpenFOAM^® libraries. Acoustic radiation is estimated using a compact source approximation of the Ffowcs Williams–Hawkings equation.It is observed that the long streamwise length scale of the inflow turbulence results in characteristic ‘humps’ in the turbine thrust and torque spectra. This effect is also evident in the far-field noise spectra. The acoustic sources on the blades are visualised in terms of sound pressure level and “Powell's source term”. These measures show that the dominant sources are concentrated at the blade leading edges towards the tip. This results from the high loading of the turbine blades, and causes the sound to radiate more akin to a monopole than a dipole.The full scale source level, obtained from scaling of the simulation results, is found to be lower than comparable measured data reported in the literature; this is attributed to additional sources not included in the present study. Based on the predicted source level, no physical impact on fish is expected.     

Conjoint-analysis-based multiattribute optimization: application in acoustical design

The concept of customer preference, or product value, prevalent in economics and management science, is just beginning to be used in engineering design. This concept and the associated measurement approaches offer us a theoretically appealing way to aggregating customer preferences for multiple product attributes into a single objective function, representing total product value, which may then be maximized. Among these methods, conjoint analysis has emerged as the most popular approach in marketing to estimate the value that customers attach to different features of a product that can be at different levels. In this paper, we use conjoint analysis in a novel way to assess a product designer’s preferences for addressing a practical problem in acoustical design. We incorporate a designer’s preferences for reducing noise in a curved pressure vessel excited with broadband noise. The shell is part of a large industrial machine. The “product” here refers to a broadband vibration absorber(s) attached to the structure. Through direct interaction with the design engineer, we elicit his/her preferences for various alternative design configurations and specify an aggregate value function. We then apply optimization techniques, interfaced to simulation codes, to maximize the value function. We show that this method provides more economical designs compared to certain conventional formulations. We conclude by summarizing some limitations to this research, which point to several future research opportunities.