一种基于多路声通道的环境噪声评估系统

系统输入端等效自噪声是声呐系统中非常重要的一项性能指标,在实际生产中一般采用低噪声环境测量法测量该指标。该方法简单便捷,但前提是获取一个低噪声的测量环境。本文提出了一种基于多路声通道的噪声评估系统对测试环境进行评估,并根据系统的反馈结果对测试环境进行针对性改善,以便更加便捷、有效地获取合格的低噪声环境。

潜艇自噪声监测系统

法国海军造船局开发了一套新型潜艇自噪声监测系统，其特点是具备从大量传感器中处理数据的能力，并且能计算出整个潜艇的辐射噪声级。计算结果是利用沿船体合理分布的传感器和测量辅机设备自噪声的传感器获得的。描述了该系统的组成，性能及其带给潜艇指挥官的诸多优点，最后还介绍了辐射噪声的计算方法。

基于光纤矢量水听器的浅海噪声矢量场特性研究

基于简正波理论分析了浅海噪声矢量场声压和质点振速的强度特性,仿真了浅海声压和质点振速的噪声强度在深度和频率上的变化特性,噪声矢量场强度特性仿真结果与实验测量结果一致。针对声场测量的有效性,给出了加速度通道自噪声谱级和灵敏度必须满足的关系式,并提出了降低自噪声对接收系统影响的两种措施。最后分析并对比了系统自噪声谱级和海洋环境噪声谱级,结果表明,声压通道的自噪声比环境噪声谱级低20 d B左右,Y通道和Z通道的自噪声比环境噪声低3.5 d B以上,X通道的自噪声谱级在200 Hz附近与环境噪声谱级最为接近,约比环境噪声低1.5 d B。

The Algorithms of Adaptive Active Noise Control Systems in a Duct

On the basis of the theory of adaptive active noise control(AANC) in a duct, this article discusses the algorithms of the adaptive control, compares the algorithm characteristics using LMS, RLS and LSL algorithms in the adaptive filter in the AANC system, derives the recursive formulas of LMS algorithm. and obtains the LMS algorithm in computer simulation using FIR and IIR filters in AANC system. By means of simulation, we compare the attenuation levels with various input signals in AANC system and discuss the effects of step factor, order of filters and sound delay on the algorithm's convergence rate and attenuation level.We also discuss the attenuation levels with sound feedback using are and IIR filters in AANC system.

Analysis and active control of low frequency booming noise in car

For Lightweight body,sound radiation and sound insulation performance have negative effects on interior noise by the deterioration of local stiffness and modality.So the research on the active control of vibration and noise for car body panels is useful for engineering.Analysis and active control of booming noise in car is researched by using a new active damping vibration reduction technology named smart constrained layer damping(SCLD).According to the vibration characters of body roof,an optimal placement of actuators is distributed.Based on dSPACE hardware in loop environment,an adaptive active control system is designed.Selecting vibration signals of engine mounting point as the reference input of adaptive controller,an active control experiment of booming noise for mini-car is carried out.Experimental results show that,when the engine speed is at 3700 RPM and4250RPM,the interior booming noise decreases 4.2dB(A),and 3.5dB(A) separately.It proposes new methods and techniques for intelligent control of car body NVH in the future.

Feedback maximization of reliability of MDOF quasi integrable-Hamiltonian systems under combined harmonic and white noise excitations

We studied the feedback maximization of reliability of multi-degree-of-freedom （MDOF） quasi integrable-Hamiltonian systems under combined harmonic and white noise excitations. First, the partially averaged Ito equations are derived by using the stochastic averaging method for quasi integrable-Hamiltonian systems under combined harmonic and white noise excitations. Then, the dynamical programming equation and its boundary and final time conditions for the control problems of maximizing the reliability is established from the partially averaged equations by using the dynamical programming principle. The nonlinear stochastic optimal control for maximizing the reliability is determined from the dynamical programming equation and control constrains. The reliability function of optimally controlled systems is obtained by solving the final dynamical programming equation. Finally, the application of the proposed procedure and effectiveness of the control strategy are illustrated by using an example.

NOISY OBSERVATION BASED STABILIZATION AND OPTIMIZATION FOR UNKNOWN SYSTEMS

The paper addresses optimization of a performance function which either is optimized via stabilizing and controlling the underlying unknown system or is directly optimized on the basis of its noise-corrupted observations. For the first case the unknown system is identified and then the indirect adaptive control approach is applied to optimize the performance function. For the second case the stochastic approximation method is used to optimize the objective function, and it appears that a number of problems arising from applications may be reduced to the one solvable by this approach. The paper demonstrates some basic results in the area, but with no intention to give a complete survey.