Radiated Noise Research Articles

Mitigation of Underwater Radiated Noise Related to Shipping and Its Impact on Marine Life: A Practical Approach Developed in the Scope of AQUO Project

There is increasing concern within the scientific community about the underwater noise due to anthropogenic activity and its impact on marine life, with negative consequences on biodiversity and sea resources. In that context, the European Marine Strategy Framework Directive stated in 2008 that the anthropogenic noise due to shipping was to be mitigated. To address this issue, the European Union (EU) project “Achieve QUieter Oceans by shipping noise footprint reduction” (AQUO) ( www.aquo.eu ) started in October 2012 with a duration of four years. The project brought together experts from shipbuilding, underwater acoustics, and bioacoustics, with a multidisciplinary approach. In this paper, after giving a brief overview of the project structure, the methodology proposed by the AQUO project to set guidelines for controlling the underwater noise from commercial shipping is presented in more detail. Such a methodology is aimed at identifying the most promising strategies for the mitigation of the impact of shipping noise on marine fauna. Different technical as well as operational solutions are evaluated by taking into account the impact on marine life, the feasibility in terms of ship design, and the cost effectiveness, also considering fuel efficiency. While technical solutions are usually more effective at the design stage both in terms of costs and performance, operational solutions can potentially be adopted without any modification to the existing fleet. Furthermore, operational prescriptions can be set by national/local authorities who cannot directly intervene on ship configurations. The different solutions have been evaluated by means of numerical modeling carried out by using a Noise Footprint Assessment Model derived from the Quonops tool.

Multi-body Dynamic Simulation and Vibro-acoustic Coupling Analysis of Bridge Crane Gearbox

A multi-rigid-body model which contains the structure system and transmission system of bridge crane gearbox is established with internal excitations such as the time-varying mesh stiffness, tooth backlash, bearing stiffness and damping and the external torque excitation caused by electric motor, and to calculate the dynamic mesh force of gears and the reaction force of bears. Then calculate the modes of the flexibility gearbox. Afterward, a vibro-acoustic coupling model of this gear system is built by taking the frequency histories of bearing reaction force as the boundary conditions, and the surface sound pressure and the radiation noise of outer sound field are calculated. The results show that the peaks of dynamic mesh force, reaction forces of bearings and dynamic responses of gearbox appear at the position of the frequency of shaft orders, mesh orders and its harmonic frequency; the maximum of radiated noise appear at 500Hz, where the surface sound pressure and the outer sound field are 82.9dB and 72.8dB.

Multiscale Sample Entropy-based Analysis of Ship Radiated Noise Signal for Surface Ship Recognition

Multiscale Sample Entropy-based Analysis of Ship Radiated Noise Signal for Surface Ship Recognition

Inversion of the Sound Speed With Radiated Noise of an Autonomous Underwater Vehicle in Shallow Water Waveguides

In December 2013, an experiment using an autonomous underwater vehicle (AUV) as a moving source for water column sound speed profile (SSP) inversion was conducted in Mogan Lake, China. With in-situ conductivity, temperature, and depth (CTD) measurements, the empirical orthogonal functions were first constructed to represent the SSP. Radiated noises of the AUV were received on a vertical line array and processed via acoustic field matching to obtain estimates of the range-independent SSP, along with the position and velocity of the AUV and the water column depth. The frequency of the radiation noise of the AUV was approximately 14 kHz. At such high frequency, even though the source motion was slow, a significant Doppler shift/broadening was observed. To incorporate the Doppler effects to better match the measured data, a forward acoustic model is derived based on the waveguide Doppler and normal mode theory. An analytical solution of the forward model is obtained for arbitrary signal integration intervals with a monochromatic source, moving radially relative to the receiver. Through simulations and experimental data processing, the feasibility of using an AUV source for water column SSP inversion has been demonstrated; it is also shown that the waveguide Doppler model is more effective compared with the model that does not consider the waveguide Doppler effect.

Predicting Modeling Method of Ship Radiated Noise Based on Genetic Algorithm

Because the forming mechanism of underwater acoustic signal is complex, it is difficult to establish the accurate predicting model. In this paper, we propose a nonlinear predicting modeling method of ship radiated noise based on genetic algorithm. Three types of ship radiated noise are taken as real underwater acoustic signal. First of all, a basic model framework is chosen. Secondly, each possible model is done with genetic coding. Thirdly, model evaluation standard is established. Fourthly, the operation of genetic algorithm such as crossover, reproduction, and mutation is designed. Finally, a prediction model of real underwater acoustic signal is established by genetic algorithm. By calculating the root mean square error and signal error ratio of underwater acoustic signal predicting model, the satisfactory results are obtained. The results show that the proposed method can establish the accurate predicting model with high prediction accuracy and may play an important role in the further processing of underwater acoustic signal such as noise reduction and feature extraction and classification.

Reduction of radiated exterior noise from the flexible vibrating plate of a rectangular enclosure using multi-channel active control

This study attempted to control the radiated exterior noise from a rectangular enclosure in which an internal plate vibrates by acoustic excitation and noise is thus radiated from that plate. Multi-channel active control was applied to reduce the vibration and external radiation of this enclosed plate. A piezoelectric ceramic was used as a distributed actuator for multiple mode control of the vibration and radiated noise in the acoustically excited plate. To maximize the effective control, an approach was proposed for attachment the piezoelectric actuator in the optimal location. The plate and internal acoustic space in the enclosure are coupled with each other. This will change dominant frequency characteristics of the plate and, thus, those of the externally radiated noise. Active noise control was accomplished using an accelerometer attached to the plate and a microphone placed adjacent to that plate as an error sensor under acoustic excitation of sine wave and white noise. It was found that the control of radiated external radiation noise requires a microphone as an error sensor, a sound pressure sensor due to vibration of the plate, differences in the dominant frequency of externally radiated noise, and complex vibration modes of the plate.

Study on Prediction of Underwater Radiated Noise from Propeller Tip Vortex Cavitation

The method to predict underwater radiated noise from tip vortex cavitation was studied. The growth of a single cavitation bubble in tip vortex was estimated by substituting the tip vortex to Rankine combined vortex. The ideal spectrum function for the sound pressure generated by a single cavitation bubble was used, also the empirical factor for the number of collapsed bubbles per unit time was introduced. The estimated noise data were compared with measured ship's ones and it was found out that this method can estimate noise data within 3dB difference.

Periodic Signal Detection in Ship Radiated Noise

Periodic signal is abundant in ship radiated noise. Its detection is an important step towards active control of ship’s acoustic signature. Based on power spectrum analysis and DEMON analysis, an approach to detect line spectrum and modulation spectrum of ship radiated noise is proposed. Periodogram method is used for power spectrum estimation. The separation of line and continuous spectrum, false positive removal, and line spectrum merging are conducted to improve the quality of detected characteristic line spectrum. Via DEMON analysis, steady physical characteristics including propeller’s rotational speed and number of blades are obtained. Finally, the effectiveness of the approach is demonstrated by simulation results.

Reduction of Underwater Radiated Noise from Ships: New Shipbuilding Challenge. The Vessels "Ramón Margalef" and "Ángeles Alvariño" as Technological References of How to Build Silent Vessels

Abatement of noise radiated by all kinds of vessels, and specially Underwater-Radiated Noise, because of its impacton marine life, has become the most outstanding novelty and the most dificult challenge the shipbuilding industryhas ever faced. Hence, the industry seeks to other new solutions to comply with the new guidelines and requirementsthat have been recently introduced and promoted by the EU, marine institutions, and the scientific community. "isnew topic, already studied and solved by the navies because of their strategic requirements, is now in the limelight andall the different aspects are being studied and discussed among the different players mentioned. In this new trend, theappearance of some class notations with “different limits”, assertions such as that the “propeller” is the major noise source,and the absence of consensus among the biological community about what should be the limits (for not affecting marine fauna), it is difficult to define the technological steps that should be followed. Until a consistent agreement is reached, the shipbuilding industry and the naval engineers will be “fighting against a ghost”. Within this “confusing scenario”, this paper is a clear example of how the Spanish shipbuilding industry is moving ahead to reduce the impact of new ships. The dynamic and acoustic design, developed by the authors, of the fishing research vessels “Ramón Margalef” and “Ángeles Alvariño” for the Oceanographic Spanish Institute and the experimental results obtained, in full compliance with ICES N°209 Underwater-Radiated Noise requirements, makes them reference vessels for the construction of “Silent Vessels”.

Study on Feature Extraction of Ship Radiated Noise Based on Cepstrum and Anti-Noise Property

Line spectrum is one kind of important feature information of the ship radiated noise, which provides a strong basis for the ship detection and identification. Due to the complexity of marine environment and the special nature of underwater acoustic channel,it is difficult to obtain ship radiated noise’ signals from the complex background noise. Under this situation, this paper proposed the cepstrum as the extraction method of obtaining feature information of the ship radiated noise, and the robust to noise performance was analyzed and compared. The analysis’ result shows that the method is simple, which is able to accurately extract feature line spectrum and shows good robust to noise.

Signatures Extraction of Ship Radiated Noise Based on Passive Sonar

By combining likelihood estimation method and Kalman filtering tracking approach, feature extraction algorithm was developed in this paper to extract the harmonic feature from the underwater noise radiated by different kinds of ships. The ability of harmonic features extrication algorithm is demonstrated by simulation and real shallow water data set comprised of a number of ships. The processing results of real data set also show that he harmonics of different kinds of ships can be used to separate from each other.

Study on the Influence Factors of Vibro-Acoustic Characteristics of Plate Structure Based on Series Approximation

To grip control mechanism of plate structure radiation noise, a method to calculate radiation resistance was improved based on series approximation, by which the analytical solution of acoustic features were derived. And then the effects of the mutual-modal coupling were investigated in studying vibro-acoustic characteristics of a simply supported plate. Some conclusions have been given, such as the relationship between the radiated noise level and the space-time distributing, fundamental principles and measures of altering the space-time distributing, which supplied the academic and applied foundation for noise control.

An Improved Passive Synthetic Aperture Sonar Alogorithm Application for Detecting of the Ship Radiated Noise

舰船辐射噪声在低频段具有稳定的线谱成分，利用该线谱成分可以实现对水下目标的检测。被动合成孔径声呐(Passive Synthetic Aperture Sonar, PSAS)技术是对小孔径基阵沿直线运动接收到的信号进行孔径合成处理，以时间增益换取空间增益，进而提高对弱目标信号的检测能力。该文中提出一种改进的被动合成孔径算法较之常规孔径合成算法不要求阵元相互重叠，综合考虑接收阵元在时间域和空间域上变化，分时间段进行处理，继而可直接进行时延补偿，理论分析结合实际仿真、海试数据综合验证算法及其性能。研究表明：改进的被动合成孔径算法具有一定有效性和可行性，且便于工程实际应用。

Target localization based on joint measurement of amplitude and frequency in a LOFAR field

To estimate the motion parameters of a moving target before its passing by the closest point of approach (CPA) point in a low frequency analyzing and recording (LOFAR) field, an error-free theoretical method based on the joint measurement of target radiated noise’s amplitude and frequency was presented. First, the error-free theoretical equations for target characteristic frequency, absolute velocity, the CPA, and amplitude of the radiation noise were derived by three equal interval measured values of the target amplitude and frequency. Then, the method to improve the calculation accuracy was given. Finally, the simulation and experiments were conducted in the air and showed the correctness of this method. By using one single piece of LOFAR, this method can calculate four target parameters and the relative error of each estimated parameter is less than 10%.

The Most Recent Noise & Vibration Assessment of the European Fleet, within the Framework of the “SILENV Project”

The EU’s new “Green Policy” to reduce the environmental impact of all types of vessels is generating new Directives that shall affect the Shipbuilding Industry. As a direct consequence, an intense debate has been opened with the participation of all the players involved: the European Commission, Marine Institutions, Shipbuilding Industry, Marine Sector, and Scientific Community. Participation of the authors in the SILENV, BESST, and AQUO projects within the FP7 has permitted noticing that for the complete assessment of the ships’ environmental impact it is essential to introduce the new so-called Noise & Vibration – Full Signature indicator. In addition to the well-known topics of Noise & Vibration (N&V) on board, it includes new ones: Noise Radiated to Harbour and Underwater Radiated Noise (URN) by the ships. Both, but especially the latter (URN) became the most outstanding novelty and the biggest challenge to be technically solved. In this sense, it is essential to know the “Starting Point”: How far is the current European Fleet from the Standard Regulations and from other Directives that will soon be compulsory? And which are the technical reasons and root causes of these deviations? To address these issues within the framework of the SILENV Project, the most recent N&V database compiled with 171 ships from the European Fleet and 12,000 N&V experimental data have been assessed. It became the largest ever N&V database in the marine sector, as well as a complete novelty. Therefore, the results, conclusions and recommendations obtained from it are of paramount importance to support current policies of the EC and other Marine Institutions that focus their efforts on combating the environmental impact of the ships.

위상 기준 스펙트럼을 이용한 드럼 세탁기 탈수 행정시의 가진력 및 방사소음 예측

Accurate prediction of the radiated noise is important to reduce the noise of the washing machine. It is also necessary to predict the excitation force accurately because excitation force can induce noise. In order to predict the excitation force acting on the washing machine, this paper conducts source identification method by use of phase reference spectrum. In this method, the transfer function between the cabinet and the motor through FEM and the measured response from the surface of the cabinet is used. The analysis of the radiation noise from the identified exciting force has been investigated. The comparison between the predicted SPL and the measured SPL at 1m apart from the front side of the washing machine showed good tendency.

Identification of Grader Radiated Noise Source Based on Partial Coherence Analysis

Partial coherence analysis can eliminate competing influences of different noise sources and identify the main noise source when all noise sources of system are relevant. In the paper, the method of partial coherence analysis is used for identifying noise source of grader. A multi-input and multi-output noise source identification model is established. And then the computational formula is developed. Finally, an experiment is carried out with an actual grader. In the experiment the main noise sources are accurately identified.

중고주파수 대역의 회전형 압축기 진동소음 해석

Power flow analysis(PFA) is introduced for solving the noise and vibration analysis of system structures in medium-to-high frequency ranges. The vibration analysis software, <TEX>$PFADS_{C++}$</TEX> R4 based on power flow finite element method(PFFEM) and the noise prediction software, <TEX>$NASPFA_{C++}$</TEX> R1 based on power flow boundary element method(PFBEM) are developed. In this paper, the coupled PFFE/PFBE method is used to investigate the vibration and radiated noise of the rotary compressor. PFFEM is employed to analyze the vibrational responses of the rotary compressor, and PFBEM is applied to analyze the radiation noise around rotary compressor. The vibrational energy of the structure is used as an acoustic intensity boundary condition of PFBEM. Numerical simulations are presented for the rotary compressor, and reliable results have been obtained.

파워흐름해석법을 이용한 상선의 수중방사소음해석

*Department of Naval Architecture and Ocean Engineering, Seoul National University, Seoul, Korea**Department of Naval Architecture and Ocean Engineering, Chonn am National University, Yeosu, KoreaKEY WORDS: Power flow analysis 파워흐름해석법, Commercial ship 상선, Underwater radiated noise 수중방사소음, Power flow finite element method 파워흐름유한요소법, Power flow boundary element method 파워흐름경계요소법ABSTRACT: Recently, the underwater radiated noises generated from large c ommercial ships have become a globally important issue. Countri es with large ports and environmental protection organizations dem and strict safety guidelines in relation to underwater radiated noise. In this paper, the coupled PFFE/PFBE method is used to investigate the vibrati on and underwater radiated noise of a commercial ship. PFFEM is employed to analyze the vibrational responses of the commercial ship, and P FBEM is applied to analyze the underwater radiation noise. The vibrational energy of the structure is treated as an acoustic intensity boundary condition of PFBEM to calculate the underwater radiation noise. Numerical simulations are presented for the commercial ship under various frequencies, and reliable results are obtained.교신저자 송지훈: 전라남도 여수시 미평로 386, 061-659-7156, jhs@chonnam.ac.kr

유한요소/경계요소 연성해석을 통한 수중 구조기인소음 해석

Radiated noise analysis from a ship structure is a challenging topic owing to difficulties in the accurate calculation of the fluid-structure interaction as well as owing to a massive degree of freedom of the problem. To reduce the severity of the problem, a new fluid-structure interaction formulation is proposed in this paper. The complex frequency-dependent added mass and damping matrices are calculated using the high-order Burton-Miller boundary integral equation formulation to obtain accurate values over all frequency bands. The calculated fluid-structure interaction effects are added to the structural matrices calculated by commercial finite element software, MSC/NASTRAN. Then, the impedance and underwater radiation noise due to an excitation of structure are calculated. The present formulation is applied to a ship to calculate the underwater radiated noise.