Liang Yu

Northwestern Polytechnical University | NWPU

The localization of cyclostationary sound sources is important for rotating machinery noise source identification and fault diagnosis. Cyclostationary sound sources are a special class of nonstationary sound sources, which exhibit periodic changes in statistics. Most of the conventional sound source identification methods are based on the stationar...

Machine Learning (ML) methods and tools have gained great success in many data, signal, image and video processing tasks, such as classification, clustering, object detection, semantic segmentation, language processing, Human-Machine interface, etc. In computer vision, image and video processing, these methods are mainly based on Neural Networks (N...

Inverse problems arise anywhere we have indirect measurement. As, in general they are ill-posed, to obtain satisfactory solutions for them needs prior knowledge. Classically, different regularization methods and Bayesian inference based methods have been proposed. As these methods need a great number of forward and backward computations, they becom...

The acoustic vector sensor (AVS) has a wide application in the direction of arrival (DOA) estimation of sound sources including aircraft, underwater or on-land vehicles, search-and-rescue efforts, etc. The performance of only one acoustic vector sensor can compare favorably with a traditional acoustic array in DOA estimation. The anisotropic noise...

The broadband acoustic modes are simulated by the following code. The point source is used as the source excitation in the duct, the axial modal basis function is set, and the collected sound pressure of the rotating array microphone is obtained to finally realize the simulation of broadband acoustic modal identification. References: [1] L. Yu, J....

This paper proposes a broadband acoustic modal identification method based on nonsynchronous measurements from a microphone array, which overcomes the acoustic modal aliasing problem caused by a limited number of microphones. In the proposed method, the number of measurement points is augmented by sequentially rotating a circular microphone array t...

Intelligent mechanical fault diagnosis techniques have been extensively developed in recent years. Owing to the advantage of data privacy protection, federated learning has recently received increasing attention; this approach can utilize monitoring data from multiple local clients to train an optimal global diagnosis model. However, low-quality da...

Keywords: Interference suppression Microphone array measurement Gaussian mixture model Variational Bayesian Closed wind tunnel measurement A B S T R A C T The microphone array is widely used in acoustics as a non-contact measurement tool, which can obtain multi-dimensional information about the sound source, such as spatial, time, and frequency. Th...

The Non-Synchronous Measurements is an efficient technique to improve the acoustic image of conventional beamforming for sound source localization. It is unable to quickly reveal the sound sources of the large machinery which requires a large synthetic array with many microphones to capture enough sound pressure data. In this paper, four Non-Synchr...

Artificial intelligence and distributed algorithms have been widely used in mechanical fault diagnosis with the explosive growth of diagnostic data. A novel intelligent fault diagnosis system framework that allows intelligent terminals to offload computational tasks to Mobile edge computing (MEC) servers is provided in this paper, which can effecti...

High spatial resolution and high accuracy acoustic source identification is valuable in the field of aircraft. Compressive beamforming is a potential method to achieve a high-quality acoustic map. However, the off-grid problem and convex relaxation loss will reduce the performance of compressive beamforming. The weighted block L1 norm regularized t...

Equivalent source method (ESM) arouses a lot of interests in the field of noise source identification and fault diagnosis. However, the performance of ESM tends to be limited by the insufficient microphones, because the size of holography plane should be larger or consistent with the sound source plane. In this paper, the non-synchronous measuremen...

The measurements of aero-engine fan noise are crucial to engine-noise reduction and silent-turbofan design. The duct mode identification is adpoted to decompose inner duct noises into spinning modes from acoustic pressure measured by a microphone array. However, modes identification of the aero-engine fan are difficult cause the number of modes is...

Rotating machinery is widely used in the modern industry, which undergoes huge amounts of variable speed working conditions. Localizing the sound sources of the rotating machinery on a specific order is significant to noise source identification and fault diagnosis. The order domain beamforming method (ODBF) is proposed in this paper to localize th...

This project aims at achieving a faster and more convenient acoustic imaging through Non-synchronous Measurements. The file named "Non-synchronous Measurement with Matrix completion" provides the faster algorithms codes including ADMM and IALM to solve the matrix completion problem converted from Non-synchronous Measurement. The file named "Nonsync...

Fault characteristic extraction of rolling bearings is essential for fault diagnosis. Rolling bearings are usually operated at changing speeds, and the nonstationary signals of the bearings are covered by the heavy background noise, making the extraction task of fault features very difficult. To address this issue, a robust fault characteristic ext...

Helicopter detection is an important part of the safety and security during flight. Most of the aerodynamic noise of modern helicopters comes from the main rotor, the main rotor aerodynamic noise thus can be used for helicopter detection. However, the Signal-to-Noise Ratio (SNR) of the measurement noise has always been quite small while the helicop...

Rotating source beamforming techniques have been effective means of noise localization on rotary machines. In this letter, we derive an alternative expression for modal composition beamforming (MCB) and subsequently consider the equivalent source assumption and cyclostationarity of the constant angular-speed rotating sound source so that a rotating...

The non-synchronous measurement (NSM) technology has been significantly developed. NSM at the coprime position (CP-NSM) is a measurement principle in two-dimensional (2D) acoustic imaging, wherein a planar array is moved to a coprime position for measurements. However, there are certain drawbacks to the measurement principles of spherical arrays in...

A multistep time domain plane wave superposition method (M-TPWM) is expanded into a new environment that the medium is fluid, and an M-TPWM with flow medium (FM-TPWM) is proposed to reconstruct the non-stationary sound field in a uniformly flow medium. In the FM-TPWM, two situations that the flow directions of the medium are parallel to and perpend...

Fast and accurate acoustic source localization methods have essential application value in the field of aircraft. Compared with traditional model-based methods, acoustic source localization technology based on deep learning shows a good application prospect. However, the uninterpretability of deep learning limits the further development of this tec...

Millimeter-wave massive multiple-input multiple-output (MIMO) vehicle-to-everything (V2X) communications can support enhanced V2X applications for connected and automated vehicles. The design of millimeter-wave V2X communications is, however, not exempt from challenges as a result of fast time-varying propagation and highly dynamic vehicular networ...

The remaining useful life (RUL) of bearings based on deep learning methods has been increasingly used. However, there are still two obstacles in deep learning RUL prediction: (1) the training process of the deep learning model requires enough data, but run-to-failure data are limited in the actual industry; (2) the mutual dependence between RUL pre...

合成孔径传声器阵列非同步测量理论和应用-概念清晰版 Synthetic Aperture Microphone Array via the Non-synchronous Measurements - Clear Concept Edition

The high-speed direct-drive blower is a high-efficiency, energy-saving, and environmentally friendly blower, and it is widely applied in industrial fields. The temperature changes significantly affect the performance of the High-speed direct-drive blower, and it is crucial to monitor its temperature. Infrared and visible light cameras are simultane...

Constraint by the physical geometry, the lower and upper frequency bound and the scale of the scanning area of a microphone array are limited. Owing to its movable feature, for the service robots, achieving a wider working frequency range with a global view requires a virtually larger and denser array, which can be realised using non-synchronous me...

Frequency-invariant (FI) beamformers play an important role in suppressing speech waveform distortions. Due to the perfect FI beampattern (FIB), differential microphone arrays (DMAs) have been widely used in practical applications like voice communication and human-machine interface systems. Superdirective beamforming generated by DMAs have many us...

The propagation of infrasound in the atmosphere is influenced by atmospheric environmental parameters, which affect the precise localization of the infrasound source. Therefore, it has become crucial to quantify the influence of atmospheric environmental parameters on infrasound propagation. First, in this paper, the tau-p model is chosen as the ph...

Harmonic denoising is one of the important preprocessing steps before extracting harmonic signal characteristics. Several signal processing techniques have been developed and applied for denoising the harmonics, which assume that the noise follows a Gaussian distribution and is stationary. However, the noise is often not so simple as a Gaussian dis...

The resolution of conventional acoustic imaging methods in a large-aspect-ratio cabin is reduced seriously by array parameters limitation and reverberation. The non-synchronous measurements technique breaks through the limitation of array shape and the number of microphones. This method can approximate the result of synthetic large-aperture array a...

The precise localization of the infrasound source is important for infrasound event monitoring. The localization of infrasound sources is influenced by the atmospheric propagation environment and infrasound measurement equipment in the large-scale global distribution of infrasound arrays. A distributed infrasound source localization method based on...

A Kalman-filter-based time-domain plane wave superposition method (KF-TDPWSM) is proposed for reconstructing the instantaneous sound field generated by a source. In the KF-TDPWSM, a discrete state formulation is first acquired using the superposition formula of time-varying pressure on a hologram plane, which forms a multiple-input and multiple-out...

The weak fault feature extraction of rolling element bearings is of critical interest for fault diagnosis. The initial fault is always very weak and buried in high background noise, making it extremely hard to extract the fault feature. Thus, it is essential to correctly extract the weak fault feature of the rolling bearings. A weak fault feature e...

Helicopter rotor aerodynamic noise research has become essential as helicopters’ reliability and comfort requirements have increased. Significant progress has been made in modeling the aerodynamically generated sound of helicopter rotors. The cyclostationary signal processing methods have been widely used for machine fault diagnosis, machinery syst...

Noise source localization of rotating machinery plays an important role in machinery noise diagnosis and control. Various beamforming methods have been developed for stationary sound source localization. However, for rotating machinery working under time-varying speed conditions, the radiated acoustic signals are typically nonstationary. Under thes...

The noise issue has become an important factor limiting the massive application of helicopters as the requirements for helicopter reliability and comfort continue to increase. As the primary noise source of helicopters, the main and tail rotor aerodynamic noise should be separated for individual noise reduction investigations. According to the freq...

This paper presents an experimental investigation of rotating source localization to identify the axial fan noise with high spatial resolution methods. It exploits the on time-domain de-Doppler, and sparsity-based inversion and the convolution model to approximate the power propagation model of the rotating source. This work is also an extension of...

A random inhomogeneous sound propagation medium is considered in acoustic imaging, which is modeled by a random function of the spatial medium. The inhomogeneity of the sound propagation environment can cause large errors in the modeling and measurement of acoustic imaging. Since the wave equation contains random variables, Green’s function no long...

The Equivalent Source Method (ESM) is a powerful technique for acoustic source reconstruction, which has been widely used in noise control and machinery fault detection. Because the inverse acoustic source reconstruction problem is typically ill-conditioned, regularization techniques are often adopted in ESM to achieve meaningful solutions. Based o...

The transformer discharge fault localization is important for the power supply reliability. The audible sound radiated by the transformer can reflect the extensive operation information. Thus, discharge faults can be localized by high spatial resolution acoustic imaging techniques to facilitate the inspection and maintenance of power equipment. In...

The transformer discharge fault localization is important for the power supply reliability. The audible sound radiated by the transformer can reflect the extensive operation information. Thus, discharge faults can be localized by high spatial resolution acoustic imaging techniques to facilitate the inspection and maintenance of power equipment. In...

为解决三维空间中声源成像分辨率低的问题,提出一种基于非同步测量的三维空间声成像方法。该方法首先通过移动球形传声器阵列扫描空间分布的声源,然后利用非同步测量技术近似得到大孔径、高密度的传声器阵列测量结果,最后通过传统波束形成算法成像。仿真及实验结果表明,该方法与单次测量下的波束形成方法相比,聚焦性能更好,空间分辨率高,可实现三维空间中声源分布的高分辨率成像;同时,该方法成像结果可替代多阵列的同步测量结果,无需参考传声器,避免了使用参考传声器在增加通道数量以及空间布置问题上的局限性。 In order to solve the problem of low resolution of acoustic imaging in three-dimensional space, a three-di...

The localization accuracy and acoustic quantification are the leading indicators of acoustic localization. It is difficult to reconstruct the acoustic field completely as the number of sources is larger than the number of microphones. To solve this problem, the sparse acoustic holography under the Bayesian framework is applied to acquire the phase...

An almost complete framework of the synthetic aperture non-synchronous measurements ...

Rolling bearings are critical to the normal operation of mechanical systems, which often undergo time-varying working conditions. When the local defects appear on a rolling bearing, the transient impulses will generate and be covered by the strong background noise. Therefore, extracting the rolling bearing weak fault feature with time-varying speed...

The microphone array can simultaneously obtain the multi-dimensional information (space-time-frequency) of sound sources, which is recognized as a fundamental and powerful tool in acoustic imaging. Acoustic Beamforming is one of the widely used methods in acoustic imaging. However, most of the applications of beamforming are based on the Gaussian n...

实验气动声学主要包含气动声学测量和气动声学信号处理。气动声学测量是气动声学研究不可或缺的手段和工具，而气动声学信号处理是气动声学测量的核心算法。气动声学信号处理的复杂性本质是气动声学的复杂性：气动声源往往是由于复杂的流动产生，并且伴随着湍流扰动和复杂结构的干涉效应以及涡流的形成和发展；其传播过程往往有着对流和非均匀的特性，同时也有声波穿过剪切层的问题；在传感器测量端往往伴随来自边界层噪声或者测量环境本底噪声强且复杂的干扰，并且亟需对应不同机理的信号分离和反演工具。本报告试图分别从气动声源、传播和测量三个维度来构建气动声学信号处理的分析框架体系：（1）针对旋转气动声源的复杂性，发展循环平稳气动声源建模理论；（2）针对传播的复杂性，发展非均匀媒质建模和不确定性量化分析手段；（3）针对测量的复杂性...

Abstract— The low-frequency sound source localization is fundamentally restricted by the array aperture. The non�synchronous measurement (NSM) is a powerful method to achieve excellent performance in low-frequency acoustic local�ization by sequentially scanning the sound field. Nevertheless, the existing methods can only perform sound source locali...

The fault feature extraction of rolling element bearings is of critical interest for fault diagnosis. The fault impulses are always buried in strong and complex background noise, which makes it hard to detect the fault characteristics and further diagnose the bearing. Many feature extraction techniques have been developed, which assumed that the no...

Acoustic wind tunnel test is an important way to study the noise mechanism of helicopter rotors. The broadband dipole noise distribution of helicopter rotors can be obtained from the acoustic wind tunnel measurement, which can be extremely helpful in analyzing the pulsation noise mechanism of rotor blade surfaces. However, during acoustic imaging o...

The noise distribution in the mechanical system is tightly connected to the structure design and particular operating conditions. The noise source localization can effectively assist with the operating condition monitoring and noise reduction design of the mechanical device. The performance limitation of the array aperture for lower frequency acous...

Rolling element bearings typically operate with fluctuating speed, leading to nonstationary vibrations. Moreover, bearings vibration signals are frequently hidden by strong distributions, making it difficult to detect clear bearing fault characteristics for diagnosis. Under this circumstance, the key issue is effectively extracting the transient fe...

Acoustic imaging from non-synchronous measurements is a powerful method that can achieve excellent performance of a densely sampled large array by using an arbitrary prototype array. It has attracted significant interest recently since it is beyond the fundamental limitation of the working frequency determined by the size and microphone spacing of...

Spinning Mode Synthesizer is an effective engine noise test rig for aero-engine noise propagation and radiation research. Spinning mode generation is realized through amplitude modulation and phase shift between individual loudspeakers. The target spinning mode is not the primary mode. It is even submerged in the undesired modes due to the system e...

提出了一种基于相位平均的旋转声源高分辨率定位方法,并给出了相位平均技术所适用的条件。为解决多普勒效应导致的旋转模糊,将旋转声信号划分成足够多个时间序列切片,在每一切片内,微小位移的旋转声源可近似等效为静止声源进行定位。其优势在于,避免了去多普勒效应的插值运算,从而保留了时域波形的相位连续性。为提高定位分辨率,运用卷积模型改造基于波束形成的能量传播模型,利用解卷积算法消除定位模糊和提高定位精度。其优势在于,卷积模型中的点扩散函数(PSF)能够建立起阵列测量与声源旋转的联系,由此通过PSF来表征麦克风阵列定位性能、分析频率对定位分辨率的影响。通过仿真信号、旋转单极子试验、风扇试验验证了方法的有效性和鲁棒性。 Here,a high-resolution localization method o...

传声器阵列信号的去噪问题对波束形成方法具有重大意义。在复杂干扰环境下,背景噪声的分布不再满足传统的互不相干假设,而更趋近于部分相干。文章研究了空间噪声的分布机理和部分相干噪声理论,并提出了一种在已知声源个数下的传声器阵列部分相干噪声的去噪方法:通过声源噪声的低秩假设以及部分相干噪声的稀疏假设,基于最优收缩方法(Opt-Shrink)迭代提取传声器阵列互谱矩阵的低秩部分,实现去噪的目的。通过仿真,验证了该方法在相干通道数为10和25时,可以获得明显的成像结果;而传统针对不相干噪声去噪的对角线移除方法(Diagonal Removal, DR)在相干通道数较多时,声源定位结果较差。在强干扰低信噪比的声源定位实验中,该方法相对于对角线移除方法可以得到更好的去噪效果。 The denoising o...

Sound source visualization has been widely used in many scenarios such as aerospace, industrial production, and urban management. Sound source localization technology plays an essential role in the realization of sound source visualization. The imaging results and calculation cost are the primary considerations in the problem of sound source locali...

本报告针对航空气动噪声测量中的声学测试方法，声源反演，气动噪声信号处理的问题，构建噪声机理、控制方程和信号处理之间的联系。发展了循环平稳气动噪声信号处理方法，解决风洞内直升机旋翼噪声测量的问题；发展了管道内高阶多模态激发方法，研制了安装多圈扬声器阵列的管道声模态发生器，可以激发截止频率以上的任意一阶或多阶周向和径向模态，解决了既有方法无法激发多个声模态的难题；发展了基于贝叶斯学习框架的涵道内宽频声模态反演方法，解决了欠定观测矩阵导致的高频声模态辨识难题。针对管道内声源辨识的需求，构建了管道内声传播模型，提出一种虚拟传声器技术，实现了基于管壁测量的管道内运动声源的高分辨率成像，进而，研究了基于管外传声器阵列测量的管道声模态辨识和声源辨识问题。

A loudspeaker is a device that converts electrical energy into acoustic energy by coupling between electrical impedance, mechanical impedance, and radiation impedance. The loudspeaker electro-mechanical-acoustic coupling model provides the experimental feasibility to measure the characteristic parameters. In this paper, an economical and practical...

In this letter, an acoustic imaging method is proposed to improve conventional non-synchronous measurements (NSM) by carrying out the NSM at coprime positions (CP-NSM). The pattern of the NSM movement is guided by a set of coprime positions. A virtual domain signal is then constructed by vectorizing the covariance matrix of the NSM. Similarly, a vi...

The acoustic imaging results in the diffuse field are seriously affected by reverberation. The acoustic source localization algorithms based on the free-field assumption will produce many artifacts in the reverberant environment. To achieve accurate acoustic source localization in a reverberant environment, a sound field morphological component ana...

作为二阶统计量的互谱矩阵(CSM)是声学成像算法的核心输入量。为增强传声器阵列的去噪表现,研究了互谱矩阵特征值滤波的机理,并提出了两种新型的特征值滤波方法的设计准则:(1)声源互谱矩阵的Stein无偏风险估计(SURE收缩),即基于SURE准则的特征值软阈值收缩;(2)进一步提高声源互谱矩阵EYM(Eckart-Young-Mirsky)估计误差的最优收缩(Opt-Shrinkage)方法,即对声源特征值所含有的噪声进一步去除。然后,在3000个快照数,0 dB信噪比(SNR),100个传声器的环境下进行仿真。通过仿真,与经典的MUSIC方法比较原声源信号与去噪后信号的互谱矩阵对角线误差,其中MUSIC方法的互谱矩阵对角线误差为74.15%,SURE收缩为41.97%,最优收缩为20.62%...

Mobile edge computing (MEC) is regarded as a promising wireless access architecture to alleviate the intensive computation burden at resource limited mobile terminals (MTs). Allowing the MTs to offload partial tasks to MEC servers could significantly decrease task processing delay. In this study, to minimize the processing delay for a multi-user ME...

Acoustic imaging is an important technique for sound source identification which is widely used in noise control and fault detection. It can be described as a method for reconstructing the amplitude and phase distribution of an acoustic field in a given plane. When the size of radiating object is huge and measurement environment is noisy, accuracy...

The resolution related with the image quality of acoustic imaging using a microphone array is limited by the size and density of the array. However, non-synchronous measurements can exceed the constraints defined by measurements with a single fixed array. The non-synchronous measurements can achieve a larger and denser aperture array by moving the...

The rotating-acoustic source localization has played an important role in rotary machine fault diagnosis, engine noise reduction and propeller recognition etc. To achieve high-resolution localization of fast rotating sources, this paper proposes an improved power propagation forward model of rotating acoustic source based on the equivalent source h...

This paper proposes a Variational Bayesian inference based on Non-synchronous Array Measurements (VB-NAM) method in order to obtain the fast and robust localization of low-frequency acoustic source. To enlarge the aperture size compared with the prototype array, the Non-synchronous Array Measurements (NAM) are performed to measure the acoustic pres...

Beamforming technology is an essential method in acoustic imaging or reconstruction, which has been widely used in sound source localization and noise reduction. The beamforming algorithm can be described as all microphones in a plane simultaneously recording the source signal. The source position is then localized by maximizing the result of the b...