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Wang, Wei-Hui. "Modelling machine induced noise and vibration in a ship structure." Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/2823.
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Most high speed vessels are fitted with powerful high speed engines which are installed in confined spacesa nd, as a consequencec, ausea n extremely high level of noise and vibration. Often structure-borne sound power is transmitted to a sound carrying structure from a source via a number of contact points. In turn, the noise and vibration are propagated in the structure and could possibly cause an undesired noise radiation. In this study, a model for predicting power flow based on the mobility theory has been addressed. The unique parts of the study include the establishment of the relationship of mobility functions with respect to four-pole parameters and the dynamic stiffness coefficients of a coupled machine/mount/foundation system. Also expressions to represent the sound input power, the output power and the transmitted power in relation to mobility functions are clarified. From a detailed analysis of relevant literature, it is shown that no validated models for predicting the propagation of structure-bome noise within the intermediate frequency range of 125 Hz to lkHz exist. As a consequence, a new numerical stress wave model has been developed to bridge this knowledge gap. This innovative approach extends the earlier works of Cremer, Heckl and Ungar in the field of stress wave propagation. Finally, a novel holistic model has been developed to line up the transmission, propagation and radiation predictions of a machine induced noise and vibration in ship's structure to take in account the fluid-structure interaction effect. A number of experiment measurements have been performed to validate the established models. From the comparisons, the prediction models are shown to be credible with an accuracy higher than 95 per cent. The established models are of a generic nature and can be applicable to diverse engineering fields regarding to the predictions of structure-borne noise and vibration transmission, propagation and radiation. Applications of these models to characterize the vibration reduction countermeasures,a s in the case of resilient mounts and squeeze-film damping plates, from a machine are also discussed.
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Raggio, Quintas Juan Pablo. "Metodologia para avaliação de ruído e vibração no corpo humano em navios de transporte de cargas perigosas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/17888.
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Este trabalho apresenta a medição e avaliação dos níveis de ruído e vibração que a tripulação de um navio, que transporta cargas perigosas na bacia do sul, está submetida e propor soluções para diminuir essa exposição. Levando em conta que a tripulação está exposta durante toda a viagem do navio a redução dos níveis de ruído e vibração é de suma importância para melhorar o conforto e a prevenção de moléstias e ou doenças decorrentes dessa exposição. Foram realizadas medições do nível de pressão sonora e aceleração nas três direções em camarotes e na praça de máquinas do navio em estudo. Foram comparadas com normas que regem os níveis de ruído e vibração adequados para embarcações marítimas. Através da análise do espectro de frequência e do espectro cruzado das medições realizadas foram definidos caminhos de propagação das ondas sonoras e vibratórias e identificadas as frequências que são transmitidas por eles. De posse desses dados são apresentadas propostas de soluções para a diminuição dos níveis de pressão sonora e vibração no navio.This work presents the measurement and assessment a ships crew exposition to noise and vibration. The ship hauls hazardous cargo in the brazilian southern basin. Considering that the crew is exposed throughout the ship's journey reducing the levels of noise and vibration is critical for improved comfort and prevention of exposure aggravated diseases. Sound pressure levels and three dimensional acceleration measurements were performed on the studied vessel's cabins and engine room. The levels of noise and vibration were compared with standards suitable for marine vessels. Propagation paths of sound waves and vibration were defined by analyzing the frequency spectrum and cross spectrum of the measurements as well as their transmitted frequencies. Proposals for based on the data gathered of sound pressure level and vibration reduction are presented.
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Moro, Lorenzo. "Structure borne noise due to marine diesel engines: experimental study and numerical simulation for the prediction of the dynamic behaviour of resilient mounts." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11114.
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2013/2014Gli alti livelli di comfort che sono richiesti oggigiorno a bordo di navi da crociera e mega-yachts, portano i progettisti a concentrare la loro attenzione sul problema del rumore strutturale. I motori diesel quattro tempi che sono installati a bordo nave come motori principali o diesel generatori, sono tra le principali sorgenti di rumore strutturale. Per questa ragione, al fine di ridurre l’energia vibrazionale generata da queste sorgenti e trasmessa, tramite le strutture nave, ai locali alloggio, i motori diesel sono sospesi mediante elementi resilienti. Tali elementi resilienti disaccoppiano la sorgente di rumore e vibrazioni (motore diesel) dal mezzo di propagazione (le strutture nave) e isolano dunque la sorgente dalle strutture riceventi. I livelli di rumore strutturale misurati alle fondazioni del motore diesel dipendono dai livelli di velocità misurati sulla sorgente (cioè ai piedi del motore diesel), dai livelli di impedenza meccanica degli elementi resilienti e dai livelli di mobilità meccanica delle fondazioni del motore diesel. Il single-point approach è un approccio semplificato per la previsione dei livelli di rumore strutturale che trascura l’interazione tra elementi resilienti. Secondo tale teoria, al fine di ridurre il rumore strutturale trasmesso attraverso gli elementi resilienti alle strutture nave, si deve ridurre l’impedenza meccanica degli elementi resilienti così come la mobilità meccanica delle fondazioni del motore diesel. In altre parole, si devono aumentare la rigidezza dinamica degli elementi resilienti così come l’impedenza meccanica delle fondazioni del motore diesel. Ad oggi, l’impedenza meccanica degli elementi resilienti può essere ricavata solo mediante prove sperimentali in laboratorio, mentre la mobilità meccanica del motore diesel è solitamente misurata quando la nave è in costruzione. Dunque non vi è la possibilità di predire, in fase progettuale, il rumore strutturale dovuto ai motori diesel. In questa tesi, viene presentata una procedura per la simulazione del rumore strutturale dovuto a motori diesel marini. La procedura si basa su test sperimentali e simulazioni numeriche. Nella prima parte della tesi sono richiamate le basi teoriche necessarie per l’esecuzione delle procedure numeriche e delle prove sperimentali. Sono dunque presentati i risultati delle analisi numeriche per simulare la mobilità delle fondazioni dei motori diesel marini. I risultati delle analisi FEM sono stati validati mediante confronto dei risultati delle analisi numeriche con i dati ottenuti da una campagna di misure eseguite a bordo nave. Successivamente sono presentati i risultati di una serie di prove eseguite per collaudare una nuova macchina sperimentale per misurare l’impedenza meccanica degli elementi resilienti. Lo scopo del collaudo era definire una procedura per l’utilizzo della macchina e per l’esecuzione di prove sperimentali in accordo alla ISO 10846, che è considerata normativa di riferimento per questo tipo di prove. Si è dunque proceduto con l’esecuzione di prove sperimentali eseguite su un elemento resiliente per motori diesel marini. Le prove sono state eseguite a differenti carichi statici. I risultati di queste prove sperimentali sono stati utilizzati per settare un modello numerico che simuli il comportamento non-lineare del componente in gomma del resiliente. I risultati ottenuti sia dalle prove sperimentali sia dalle simulazioni numeriche sono stati utilizzati per predire il rumore strutturale generato dai motori diesel, in accordo al single-point approach. I risultati ottenuti dall’applicazione del metodo sono stati confrontati con misure eseguite a bordo e sono stati discussi per evidenziare vantaggi e svantaggi dell’applicazione del metodo. Le procedure numeriche per la simulazione del comportamento dinamico del resiliente e della fondazione costituiscono un primo passo per l’ottimizzazione del sistema di isolazione del motore diesel marino.
The high level of comfort that is required today on board cruise vessels and mega-yachts, leads the designers to focus their attention on structure-borne noise issues. Four-stroke diesel engines that are installed on board as main diesel engines for the propulsion system and as gen-sets, are usually the main sources of structure-borne noise. For this reason, the diesel engines are usually resiliently mounted in order to reduce the vibration energy generated by these sources and transmitted through the ship structures to the accommodation areas. These mounts decouple the noise and vibration source (diesel engine) from the means of wave propagation (ship structures) and so, they isolate the source from the receiving structures. The structure-borne noise levels measured at the diesel engine foundation depend on the velocity levels measured at the source (diesel engine feet), on the mechanical impedance levels of the resilient mounts and on the mechanical mobility levels of the diesel engine foundation. The simplified theory of the single-point approach neglects the interaction among the resilient mounts. According to this theory, to decrease the structure-borne noise transmitted through the resilient mounts towards the ship structures, the mechanical impedance of the resilient mounts as well as the mechanical mobility of the diesel engine foundation are to be lowered. In other words the dynamic stiffness of the resilient mounts has to be decreased and the mechanical impedance of the diesel engine foundation has to be increased. To date, the mechanical impedance of real resilient mounts can only be obtained by laboratory tests and the mechanical mobility of the diesel engine foundation is usually measured when the ship is under construction, so it is not available for predictive analyses. In the thesis, a procedure for simulating the structure-borne noise generated by marine diesel engine is discussed. The procedure is based on both experimental tests and numerical simulations. In the first part of the thesis, some notes on the theoretical background are presented. Then, the results of FE analyses for simulating the mechanical mobility of a diesel engine foundation are shown. The FE models have been validated by the results of a measurement campaign carried out on board a ship. Then, the results of a series of tests performed to tune a new test rig, designed and built up at the University of Trieste for measuring the mechanical impedance of resilient mounts, are discussed. The campaign for tuning the test rig has been carried out in order to set an experimental procedure that allows achieving results in compliance with the ISO 10846 Standard, which is a sound reference for this kind of tests. As a case study, a large resilient mount for marine diesel engines has been tested to achieve its mechanical impedance curve at different static pre-loads. The outcomes of the experimental tests have been used for tuning the best numerical model of the resilient mount that properly takes into account the nonlinear behaviour of the rubber core. The data of the experimental tests carried out on board ships as well as in laboratory and the outcomes of numerical simulations have been used to predict the structure-borne noise according to the single-point approach. The outcomes achieved by the application of the method have been compared with on board measurements and pros and cons of the method are widely discussed. Moreover, the numerical procedures for the simulation of the dynamic behaviour of the resilient mount and the diesel engine foundation, pave the way for the optimization of the decoupling system of marine diesel engines.
XXVII Ciclo
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Velonias, Platon Michael. "Vibration analysis of a SWATH-type ship." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38129.
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Graham, William Richard. "Boundary-layer noise and vibration." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308331.
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Körning, Ljungberg Jessica. "Psychological responses to noise and vibration." Doctoral thesis, Umeå universitet, Folkhälsa och klinisk medicin, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-915.
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Vehicle drivers are a group of workers that are exposed to noise and whole-body vibration (WBV) several hours a day. Some drivers may also be exposed to high mental loads – monitoring and manipulating physical controls while engaging problem solving activities often with strong short-term memory and spatial manipulation components. Present standards and regulations that govern health risk assessment do not take into consideration the complexities of these multiple exposure environments. The effect of one factor (for example, noise or WBV) may be different than the effect of two factors presented together. This thesis investigates whether the combination of noise and WBV affects the performance of cognitive tasks more than when the exposures are presented separately. A series of studies were designed to expose subjects to noise and WBV stimuli designed to simulate real life working conditions. Different combinations of subjective ratings, cognitive tests, and cortisol measurements were conducted both during and immediately after exposures, which ranged from 20 to 45 minutes. The studies have shown that a combination of noise and WBV do not degrade cognitive performance more than a single stimulus. However, WBV can degrade attention performance after exposure is turned off when drivers have been working under high mental load during exposure. The combined stimuli are also experienced as more annoying and work is more difficult in such conditions. The exposure times and task difficulty levels used in this thesis did not produce biological stress as measured by cortisol. Nevertheless, subjective ratings are sometimes seen as early indicators of other symptoms and with increased task difficulty and/or longer exposure times there may appear other measurable outcomes of the combined stimuli.
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Körning, Ljungberg Jessica. "Psychological responses to noise and vibration /." Umeå : Umeå universitet : Arbetslivsinstitutet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-915.
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Tratch, Jorge. "Vibration transmission through machinery foundation and ship bottom structure." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15216.
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Thesis (Mech.E)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Includes bibliographical references.
by Jorge Tratch Junior.
Mech.E
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Huang, Yuan. "Human response to combined noise and vibration." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348814/.
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The discomfort caused by the noise and vibration in cars is investigated in this thesis to improve understanding of how subjective judgements of noise and vibration affect each other, how the relative discomfort of noise and vibration depend on their magnitudes and their durations, and how the total discomfort caused by simultaneous noise and vibration can be predicted. Two experiments were designed to determine the magnitude-dependence of the relative discomfort caused by noise and vertical whole-body vibration. Subjects were presented with various combinations of different levels of noise and different magnitudes of vibration, and rated the discomfort caused by noise relative to the discomfort caused by vibration, and also vibration discomfort relative to noise discomfort. The subjective equivalence between noise and vibration was highly dependent on whether noise was judged relative to the vibration or vibration was judged relative to the noise. When judging noise, higher magnitude vibrations appeared to mask the discomfort caused by low levels of noise. When judging vibration, higher level noises appeared to mask the discomfort caused by low magnitudes of vibration. The duration-dependence of the relative discomfort of noise and vibration was then investigated. Subjects were presented with 49 combinations of seven levels of noise and seven magnitudes of vertical whole-body vibration, and with five durations (2, 4, 8, 16, and 32 s). Either the discomfort caused by noise relative to the discomfort caused by vibration, or vibration discomfort relative to noise discomfort were rated in two sessions. The findings indicate that noise discomfort and vibration discomfort have a similar dependence on duration. The slopes expressing the levels of noise (sound pressure level or sound exposure level) judged equivalent to the levels of vibration (logarithms of the r.m.s. acceleration or vibration dose value) increased with increasing duration when judging noise relative to vibration, but were independent of duration when judging vibration relative to noise. As the durations increased from 2 to 32 s, the masking effect of vibration on noise discomfort decreased, whereas the masking effect of noise on vibration discomfort did not change. Finally the noise discomfort in the presence of vibration, vibration discomfort in the presence noise, and the combined discomfort of simultaneous noise and vibration were investigated by employing the method of absolute magnitude estimation. Subjects judged noise discomfort, vibration discomfort, and their total discomfort in different sessions. The results suggest that, within the range of stimuli magnitudes investigated, the discomfort caused by vibration was reduced by noise whereas the judgement of noise discomfort was not significantly influenced by vibration. The total discomfort caused by simultaneous noise and vibration was well predicted by ψc = [(ψv)2+ (ψs)2]0.5, where ψv, ψs, and ψc, represent vibration discomfort, noise discomfort, and their total discomfort, respectively. In conclusion, the relative discomfort caused by noise and vibration varies according to whether subjects are asked to judge noise discomfort relative to vibration discomfort or vibration discomfort relative to noise discomfort. There are masking effects of noise on the judgement of vibration discomfort, and of vibration on the judgement of noise discomfort, depending on the relative magnitudes of the two stimuli. The influence of vibration on the judgement of noise discomfort decreases with increasing duration of the stimuli, whereas the influence of noise on the judgement of vibration discomfort is independent of the duration. The discomfort caused by a combination of noise and vibration can be predicted by root-sums-of-squares of the discomfort caused by noise and the discomfort caused by vibration when these stimuli are presented alone.
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Lin, Tian Ran. "Vibration of finite coupled structures, with applications to ship structures." University of Western Australia. School of Mechanical Engineering, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0093.
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[Truncated abstract] Shipbuilding is fast becoming a priority industry in Australia. With increasing demands to build fast vessels of lighter weight, shipbuilders are more concerned with noise and vibration problems in ships than ever. The objective of this thesis is to study the vibration response of coupled structures, in the hope that the study may shed some light in understanding the general features of ship vibration. An important feature characterizing the vibration in complex structures is the input mobility, as it describes the capacity of structures in accepting vibration energy from sources. The input mobilities of finite ribbed plate and plate/plate coupled structures are investigated analytically and experimentally in this study. It is shown that the input mobility of a finite ribbed plate is bounded by the input mobilities of the uncoupled plate and beam(s) that form the ribbed plate and is dependent upon the distance between the source location and the stiffened beam(s). Off-neutral axis loading on the beam (point force applied on the beam but away from the beam’s neutral axis) affects the input power, kinetic energy distribution in the component plates of the ribbed plate and energy flow into the plates from the beam under direct excitation ... solutions were then used to examine the validity of statistical energy analysis (SEA) in the prediction of vibration response of an L-shaped plate due to deterministic force excitations. It was found that SEA can be utilized to predict the frequency averaged vibration response and energy flow of L-shaped plates under deterministic force (moment) excitations providing that the source location is more than a quarter of wavelength away from the plate edges. Furthermore, a simple experimental method was developed in this study to evaluate the frequency dependent stiffness and damping of rubber mounts by impact test. Finally, analytical methods developed in this study were applied in the prediction of vibration response of a ship structure. It was found that input mobilities of ship hull structures due to machinery excitations are governed by the stiffness of the supporting structure to which the engine is mounted. Their frequency averaged values can be estimated from those of the mounting structure of finite or infinite extents. It was also shown that wave propagation in ship hull structures at low frequencies could be attenuated by irregularities imposed to the periodic locations of the ship frames. The vibration at higher frequencies could be controlled by modifications of the supporting structure.
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Lin, Tian Ran. "Vibration of finite coupled structures, with applications to ship structures /." Connect to this title, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0093.
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Godaliyadde, Darshana. "Application of formal safety assessment for ship hull vibration modelling." Thesis, Liverpool John Moores University, 2008. http://researchonline.ljmu.ac.uk/5898/.
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This research has evaluated the rules, guidelines and regulations related to ship vibrations. A historical failure data analysis is carried out to identify associated components, equipment and the areas of defects related to ship vibration problems. Ship Hull Vibration (SHV) is recognised as a major problem onboard ships and the propulsion system is identified as the major contributor to SHV. The current status of ship vibrations is reviewed and possible sources which create SHV are recognised. The major problems identified in this research are associated with risk modelling under circumstances where high levels of uncertainty exist. Following the identification of research needs, this PhD thesis has developed several analytical models for the application of Formal Safety Assessment (FSA). Such mode quently demonstrated by their corresponding case sti vith regard to application of FSA for SHV modelling. Firstly, in this research a generic SHV model is constructed for the purpose of risk estimation based on the identified hazards. The hazards include the SHV effects induced by ship design criteria, failure of components, and different patterns associated with the ship propulsion system (propeller system and machinery) as the major contributors to SHV. Then risk estimation bn is carried out utilising Evidential Reasoning (ER) and a fuzzy rule base. Secondly, ship selection (decision making) is investigated to to select the best ship design based on the risk estimation results of SHV. The risk estimation is carried out using ER, a fuzzy rule base and continuous fuzzy sets. The best ship design is selected by taking into account an ER-based utility ranking approach. Thirdly, combining discrete fuzzy sets and an Analytical Hierarchy Process (AHP) risk estimation is conducted in terms of four risk parameters to select the major causes of component failure and then SHV.
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Akl, Wael Nabil. "Smart foam for active vibration and noise control." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/222.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2004Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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O'Boy, Daniel John. "Tyre/road noise : vibration of the tyre belt." Thesis, University of Cambridge, 2005. https://www.repository.cam.ac.uk/handle/1810/251965.
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Randle, Perri. "Noise and Vibration Control for a Decanting Centrifuge." Thesis, University of Canterbury. Mechanical, 2011. http://hdl.handle.net/10092/5987.
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High levels of machine noise result in health issues for those people exposed to the machine for extended periods. Machine noise is becoming a more significant design consideration, often because of legislative requirements.
Decanting centrifuges are machines with a rotating bowl. They have a number of noise sources, the most significant being structural noise, vortex/turbulence noise and siren noise. Due to the size, mass and speed of the rotating bowl, the bowl is the main source of structural noise. The structural noise is produced by all surfaces that are directly coupled to the bowl’s bearings. Due to the speed of rotation of the bowl, the turbulence from the various trailing edges generates broad spectrum vortex noise. Siren noise due to air flow through the bowl also generates significant noise especially at the lower harmonics of the bowl rotation frequency.
Strategies to reduce decanter machine noise include:
• Decoupling the surfaces of the from the main bearings of the rotating bowl and hence reduce the amount of structurally transmitted noise.
• Smoothing the surface of the bowl to minimise the edges that produce vortices that are shed and produce vortex/turbulence noise.
• As siren noise is produced due to flow through the rotating bowl, which is integral to the function of the decanter, the exit ports should be designed so that the noise is produced within parts of the sound spectrum that have low noise levels.
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Winberg, Mathias. "Noise and Vibration Control of Combustion Engine Vehicles." Doctoral thesis, Karlskrona : Blekinge Institute of Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00281.
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Noise and vibrations have over the last two decades been regarded as significant environmental health problems. Regulations regarding acoustic as well as vibration levels have therefore become more stringent. This thesis embraces two different techniques to reduce unwanted noise and vibrations, spectral subtraction and active noise and vibration control. The applications treated for noise and vibration problems are mainly means of transportation driven by combustion engines as for example, helicopters, boats, and cars. All these vehicles have low-frequency noise and vibration problems which are difficult to solve by means of passive isolation, hence alternative methods must be sought. Two different scenarios are studied. First, the high noise level in the interior of the vehicle is accepted and the humans inside are equipped with headsets utilizing both passive as well as active noise control. If the means of transportation employs some kind of communication equipment, such as for a cellular telephone or an intercom radio, the noisy speech signal picked up by the microphone is cleansed by spectral subtraction, which is a non-linear filtering method employed in the frequency domain. In the second scenario the entire interior of the vehicle is subjected to noise and vibration reduction by means of active noise and vibration control. Active noise and vibration control is the art of reducing a primary sound or vibration field by interference with a secondary anti-field. The thesis focus on real-life applications which implies that a lot of measurements and practical difficulties must be treated for both scenarios, especially in the area of active noise and vibration control. In this area, the basic idea seems straight-forward, but implementing it in large and complex structures, such as vehicles, is extremely difficult, in particular if high attenuation is required.
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Long, Stephen Andrew. "Acoustic noise and vibration of switched reluctance machines." Thesis, University of Sheffield, 2002. http://etheses.whiterose.ac.uk/14498/.
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This thesis describes a systematic investigation into the sources of acoustic noise and vibration in switched reluctance machines, and encompasses the vibrational behaviour of the stator, the influence of control parameters, and an evaluation of the effectiveness of active vibration cancellation. The influence of leading design parameters, such as the width and number of poles and the yoke thickness, and geometric asymmetries, such as lamination notches in the stator core, and the effect of the stator windings, the frame, the end-caps and the mounting assembly, on the natural frequencies and modes of vibration are investigated, Chapter 3. Both two-dimensional and three-dimensional finite element analyses are employed, the predicted results being validated by measurements on various experimental models, which consequently highlights the limitation of the finite element technique for highly complex structures with discontinuities in their fabrication. The influence of the mass and stiffness of the laminated stator core and the stator windings on the natural frequencies and vibration modes is investigated, and effective material properties are deduced for the analyses. It is found that the number of poles and lamination notches on the stator influence the number of vibrational modes which occur in the audible frequency range due to the introduction of dual natural frequencies, viz. symmetrical and anti-symmetrical modes, which are shown to separate further in value as the asymmetries become more profound. As the diameter of the stator yoke is reduced the natural frequencies increase, whereas increasing the thickness of the yoke and the adding of a frame and end-caps significantly increase the natural frequencies. The effect of the stator poles is to significantly reduce the stator natural frequencies, which are irrespective to a variation to the width of the poles, a variation in their mass being annulled by the resulting change in stiffness. Similarly, it is shown that the winding mass and stiffness offset each other so that their influence is also relatively small, whereas, although quantification of the damping is not within the aims of this thesis, it is apparent that the windings introduce a high level of damping which consequently limits the magnitude of the vibrations and hence acoustic noise. Finally, the laminated nature of the core is quantified and is shown to affect the effective material properties compared to an equivalent solid core, and to increase the effective damping. Previous investigations have studied the influence of the drive control parameters, but generally limit the analysis to either the frequency or time domain or to measurements of the sound pressure level, and are generally carried out in isolation. Therefore. the influence of alternative operating modes and their associated control parameters on the acoustic noise and vibration of an SR machine is thoroughly investigated. the results being analysed in both the frequency and time domains, and compared with measurements of the sound pressure level, Chapter 4. The noise and vibration which results when the SR machine is operated under both voltage and current control. with both hard and soft chopping techniques, and various switching angles, and for various sampling and switching frequencies, is measured. The influence of speed and load is also investigated, and the vibration and noise are also investigated under single pulse mode operation. It is found that hard chopping results in a noisier operation than with soft chopping due to increased current ripple, especially under current control. The noise and vibration is clearly shown to differ under current control compared to voltage control and single pulse mode, due to the random switching of the phase voltages resulting in wideband harmonic spectra, thereby increasing the levels of all the mechanical resonances. Further, it is found that the noise and vibration increase with both speed and load. In general, the increases in noise and vibration are attributed to an increase in the rate of decay of current at phase turn-off, regardless of the control parameter under investigation. Finally, the effectiveness of active vibration cancellation for nOIse reduction is investigated under typical operating modes in Chapter 5, which, for the first time, is analysed in both the frequency and time domains, and validated by measurements of the sound pressure level. It is found that active vibration cancellation is less effective for machine stators which have more than one dominant vibration mode within the audible frequency range, since the technique is only capable of applying active cancellation for a single vibration mode, thus any further resonances remain unaffected. Further, during chopping control, especially current control which results in random switching, it has been shown, for the first time, that the effective time-delay varies to that applied, thus rendering the technique less effective. This is found to be attributed to the asynchronism of the final chopping edge and point of phase turn-off, therefore preventing the vibrations from being excited in anti-phase, as explained in section 5.6.
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Schaberg, P. W. "Knock-induced noise and vibration in I.C. engines." Thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/23513.
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Dayou, Jedol. "Global control of flexural vibration of a one dimensional structure using tuneable vibration neutralisers." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310842.
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Jha, Akhilesh K. "Cyclostationary Random Vibration of a Ship Propeller and a Road Vehicle." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34486.
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A special class of nonstationary processes with periodically varying statistics, called cyclostationary (CS), is investigated. These processes are encountered in many engineering problems involving rotating machinery such as turbines, propellers, helicopter rotors, and diesel engines. We analyze a cyclostationary process model in order to show its advantages compared to a traditional stationary process model and present a methodology for calculating the statistics of the response of a linear system subjected to CS excitations.
We demonstrate that a CS model estimates the statistics of the response of a linear dynamic system subjected to CS excitations more accurately by considering (1) a vehicle traveling on a rough road and (2) a propeller rotating in the wake of a ship in the presence of turbulence. In the case of the vehicle, the road consists of concrete plates of fixed length. We model the road excitation using a CS process and calculate the standard deviation (root mean square) of the vehicle response. In the case of the ship propeller, we calculate the hydrodynamic forces acting on the propeller using the vortex panel method and the vortex theory of propeller. Considering the randomness in the axial and the tangential components of velocity, we calculate the mean and the covariance of the forces. This analysis shows that the hydrodynamic forces acting on the propeller are CS processes. Then we perform finite element analysis of the propeller and calculate the mean and the standard deviation of the blade response. We do the parametric analysis to demonstrate the effects of some physical quantities such as the standard deviation, the correlation coefficient, the decorrelation time, and the scale of turbulence of the axial and the tangential components of the wake velocity on the standard deviation of the blade deflection. We found that the CS model yields the time-wise variation of the statistics of the excitation and the response (e.g., the root mean square) and their peaks correctly. This is important information for the calculation of probability of failure of the propeller. A traditional stationary model cannot provide this information.Master of Science
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Matusiak, Jerzy. "Pressure and noise induced by a cavitating marine screw propeller." Espoo : Valtion teknillinen tutkimuskeskus, 1992. http://catalog.hathitrust.org/api/volumes/oclc/25913793.html.
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Cheng, Yi. "Acoustic noise and vibration of brushless motors for fans." Thesis, University of Leicester, 2005. http://hdl.handle.net/2381/34751.
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An investigation on vibration and acoustic noise on brushless motors for fan or blower applications is presented, particularly concentrating on the vibration due to electromagnetic origin within the brushless electronically commutated motors. The flux switching motor is introduced as a relatively new class of reluctance machine, which retains the benefits of switched reluctance machines, but with simpler and cheaper power electronic converters. The novel work of this thesis is the introduction of two 8/4 flux switching motors with permanent magnets of internal rotor and external rotor configuration respectively, which are presented as alternatives for the brushless DC motor, and called the permanent magnet flux switching motor. The two new permanent magnet flux switching motors were able to show potential in reducing power consumption, reducing vibration and noise, and reducing the cost of the power electronic drive when compared with an existing commercial 3-phase brushless DC and induction motor. Investigation on the vibration and noise of the flux switching motor was also done by performing experiments, mechanical finite element analysis and algebraic frequency equation analysis. Algebraic frequency equations were implemented into the electromagnetic design environment, stressing the need and potential in having algebraic frequency equations to predict the mechanical resonant frequency of any shape of the electrical machine stator lamination in the electromagnetic design environment.
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Howarth, Henrietta Victoria Carmel. "Annoyance caused by railway vibration and noise in buildings." Thesis, University of Southampton, 1989. https://eprints.soton.ac.uk/52250/.
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This thesis is concerned with the annoyance caused by railway-induced building vibration and railway noise. A review of previous studies was conducted to examine current knowledge. The review enabled identification of areas in which there was insufficient information on which to base a prediction of the reaction to railway vibration and noise in buildings. Deficiencies in current knowledge formed the basis of a programme of experimental work which was conducted to investigate how the annoyance produced by railway-induced building vibration is affected by the number of trains, the vibration magnitude, the vibration frequency, the direction of vibration and the presence of noise. Two laboratory experiments were concerned with how annoyance caused by railway-induced building vibration depends on the magnitude of vibration and on how often trains pass. A trade-off was determined between the number of trains and the vibration magnitude which indicated a fourth power relation between magnitude and duration. The relation supports the use of the vibration dose value as a method of vibration assessment. Two further experiments were conducted to determine the subjective equivalence of noise and vibration and to investigate the interaction and combined effects of the two stimuli. The results suggest that vibration does not influence the assessment of noise but that the assessment of vibration can be increased or reduced by the presence of noise, depending on the relative magnitudes of the vibration and noise. A fifth experiment was performed to investigate the influence on annoyance of vibration frequency, vibration magnitude and vibration direction. Vibration frequency weightings were determined to describe subjective response to whole-body vibration at low magnitudes such as occurs in buildings. The results indicate that the weightings in British Standard 6841 (1987) provide a reasonable approximation to the frequency dependence of response to whole-body vibration at low magnitudes. In the final experiment the previous findings were combined to provide a general method of predicting the relative annoyance from complex conditions of railway vibration and noise. The method was shown to provide a more accurate prediction of the relative annoyance from railway vibration and noise than methods based on the influence of noise or vibration alone.
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Guo, Ningqun. "The vibration characteristics of piezoelectric discs." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/11449.
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Vipperman, Jeffrey S. "Adaptive feedforward control of broadband structural vibration." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-12302008-063428/.
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Munn, Jacqueline Marie. "Virtual sensors for active noise control /." Title page, abstract and table of contents only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phm9668.pdf.
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Jasti, Srichandana. "Design of randomly placed microphone array." Birmingham, Ala. : University of Alabama at Birmingham, 2006. http://www.mhsl.uab.edu/dt/2006m/jasti.pdf.
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Forrest, James Alexander. "Modelling of ground vibration from underground railways." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323675.
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Alexiou, Kimon. "Comparison of multi-point vibration test methods." Thesis, Queen Mary, University of London, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325279.
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Newman, M. J. "Active vibration control using a distributed controller." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262146.
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Wang, Anbin. "Vibration analysis of fluid filled pipework systems." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323805.
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Nelson, Cory Lee. "Reducing phase noise degradation due to vibration of crystal oscillators." [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1476330.
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Lo, Chun Sing. "Application of cementitious rubber chips as noise and vibration barriers /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20LO.
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朱炳年 and Ping-nin Raymond Chu. "The vibration and noise radiation characteristics of damped sandwich structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31231123.
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Esgandari, Mohammad. "Simulation methods for vehicle disc brake noise, vibration & harshness." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5762/.
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After decades of investigating brake noise using advanced tools and methods, brake squeal remains a major problem of the automotive industry. The Finite Element Analysis (FEA) method has long been used as a means of reliable simulation of brake noise, mainly using the Complex Eigenvalue Analysis (CEA) to predict the occurrence of instabilities resulting in brake noise. However it has been shown that CEA often over-predicts instabilities. A major improvement for CEA proposed in this study is tuning the model with an accurate level of damping. Different sources of damping are investigated and the system components are tuned using Rayleigh damping method. Also, an effective representative model for the brake insulator is proposed. The FEA model of the brake system tuned with the damping characteristics highlights the actual unstable frequencies by eliminating the over-predictions. This study also investigates effectiveness of a hybrid Implicit-Explicit FEA method which combines frequency domain and time domain solution schemes. The time/frequency domain co-simulation analysis presents time-domain analysis results more efficiently. Frictional forces are known as a major contributing factor in brake noise generation. A new brake pad design is proposed, addressing the frictional forces at the disc-pad contact interface. This concept is based on the hypothesis that variation of frictional coefficient over the radius of the brake pad is effective in reducing the susceptibility of brake squeal.
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Oppenheimer, Charles Hugh. "Impact-induced noise and vibration in machine systems for design." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12614.
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Luo, Jian. "Frequency domain iterative tuning for active noise and vibration control." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/63858/.
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In this thesis a new adaptive control method, called Iterative Tuning in the Frequency Domain (FD-IT), is proposed for Active Noise and Vibration Control (ANVC). This approach is a gradient based self-tuning method which completely relies on analysis of the frequency response of system dynamics and the spectrum of signals. The new method is based on a new gradient estimation theory in the frequency domain. In this theory the gradient of the output spectrum with respect to controller parameters is expressed with the frequency response of dynamics and the spectrum of signals. When the performance gradient with respect to controller parameters can be expressed as some function of the signals’ spectrum, it can be computed out completely in the frequency domain. Similar to audio compression, when the system’s signals contain few frequencies, the computation of performance gradient can be greatly simplified by making ”partial modelling” with respect to those frequencies. According to the proposed theory, the new iterative tuning method, i.e., FD-IT, is developed for ANVC problems with periodic disturbances. It can tune the feedback/feed-forward controllers simultaneously with one experiment per iteration except some extra experiments for initial tuning. It covers both Single Input Single Output (SISO) and Multiple Input Multiple Output (MIMO) systems. Furthermore, it can be extended to nonlinear systems as well. Some issues about the implementation of the iterative method are discussed. Through the comparison with some other popular active control methods in ANVC, the advantages of the new method, including: the flexibility in selecting controllers, the simplicity in control structure, and the convenience in implementation, are emphasized. The effectiveness and robustness of the proposed iterative tuning method are tested through simulated SISO and MIMO Linear Time Invariant (LTI) systems. Two simulated nonlinearities are used to illustrate the usefulness of the methods in nonlinear system as well. To show the practicability, the linear and nonlinear FD-ITs are implemented in an air-duct system with a PC-DSP based agent-architecture. All the results illustrate that FD-IT is an easy and effective approach to solve ANVC problems with periodic disturbances.
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Harne, Ryan. "Novel Lightweight Noise and Vibration Control Treatments for Marine Structures." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34621.
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This thesis presents the development and testing of distributed vibration absorber designs with specific application to heavy plates for the reduction of vibration and sound radiation. Two particular designs, already under investigation for use on thin panels or composite materials, were adapted to passively reduce broadband vibration and noise from large and heavy plates. These absorbers are referred to as Distributed Vibration Absorbers [DVAs] and Heterogeneous [HG] Blankets. Numerical models were developed, based on the theory of sound propagation through layered media and the vibration of plates, to simulate the performance of such absorbers for a variety of applications and media characteristics. The new absorber designs were then tested on a large, marine-type plate (4 feet by 2 feet by 1/4 inch) and showed both broadband noise and vibration control from 60 Hz to 5 kHz. DVAs could reduce the vibrating plate resonance magnitudes on the order of 15 dB at their tuning frequencies while providing overall vibration reduction of 5 dB or greater at higher frequencies. HG blankets were also capable of reducing plate resonance vibration up to 15 dB at their tuning frequencies and produced overall vibration reduction of 5 dB at higher frequencies. These absorbers are entirely passive, i.e. requiring no controller or prior modal testing of the structure, were placed randomly during testing, and are designed to contribute less than 10% additional mass to the structure, making them a robust vibration and noise control solution.Master of Science
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Wright, Richard I. "A Hierarchical Noise Control System Using Adaptable Tuned Vibration Absorbers." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11217.
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A novel noise control system is developed using adaptable tuned vibration absorbers (ATVA) to interact with a vibrating host structure in such a way as to reduce radiated acoustic energy. ATVA's are single-degree-of-freedom resonant devices that can change their resonant frequency and damping over a range. This ATVA noise control system is targeted at applications with tonal disturbances such as propeller aircraft. The motivation for this work is to better understand and experimentally demonstrate the noise control performance of globally detuned vibration absorbers (i.e. tuned away from the disturbance) compared to that of perfectly tuned devices on complex structures. A two-tier hierarchical control approach is used where a global control algorithm attempts to minimize a global parameter such as radiated acoustic energy by directing the adaptation of subordinate ATVA's. The global control algorithm uses an adaptive simplex search algorithm that requires no initial knowledge of the structure or the ATVA's. The ATVA's also require no model of the structure, each utilizing only the local vibration of its own mass and control gains set by the global controller. Noise control using a single ATVA is first studied on a small simply supported plate. Then, a multiple ATVA system is tested on a large plate structure at several test frequencies where many structural modes participate. Noise reductions up to 22 dB are achieved at locations in the radiated field. Further, it is found in some cases, classic tuning of the ATVA results in increased structural noise radiation. ATVA's are realized by outfitting typical inertial (proof-mass) actuators with a classical feedback loop. The device's resonant frequency and damping can be controlled independently, yet simultaneously via two control gains. The ATVA's are designed, built, and characterized for their adaptable domain and power requirements. A cohesive analytical model of the ATVA is also developed and used to compliment the experimental results.Ph. D.
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Kim, Seungbo. "Structure-borne noise transmission through a multi-dimensional vibration isolator /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486399451959589.
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Cahill, John J. "Experimental studies of noise/vibration damping for undersea warfare applications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FCahill.pdf.
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Chu, Ping-nin Raymond. "The vibration and noise radiation characteristics of damped sandwich structures /." [Hong Kong] : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12223001.
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Rule, Ruth Anne. "Vibration-based damage detection in ceramics and glass." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/27153.
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This thesis describes the development of the hardware, experimental procedures and algorithms required for vibration based damage identification in small ceramic and glass structures. The results form the basis of a fully automated industrial quality assurance system.
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Ananthaganeshan, Kanapathipillai Arunachalam. "Stability and performance of active vibration isolation systems." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273915.
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Wei, David, and 魏宏源. "Ship Hull Vibration And Its Underwater Radiated Noise." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/95307575782451055935.
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碩士國立臺灣大學
造船工程學系
81
The main goal of this paper is to determine the dominant source of the underwater noise radiated from a surface vessel at mid-frequency range. We find that it is not the "MACHINE-NOISE" but the "FLUID -NOISE" resulted from thep propeller. This could be demonstrated by the following arguement according to the experimental data : (1) The amplitude of the plate vibration of the side wall in the machine room of the ship and the water , did not increase with the increasing of rotating speed of the main engine ,that is, the underwater radiational noise induced by the main engine is NOT significant in the ship''s underwater ship noise. (2) When the hull plate of the A.P. part of the ship is forced by the "FLUID-NOISE" ,there is a wide-band noise observed in the far- field pressure field . The near-field pressure at the wet side of the hull plate of A.P part is predicted by "GALERKIN METHOD " and " MIN. ERROR METHOD ".the resonat mode of plate vibration is not in the far-field measured data while it exits in the near-field theoretical predication.
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Shuh, Dino, and 束文龍. "Ship Vibration Transmission and the Prediction of Underwater Noise." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/14552132360696163870.
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碩士國立海洋大學
造船工程學系
82
In this report, we use the Statistical Energy Analysis method to calculate the ship vibration transmission and the underwater noise due to the engine vibration. An engine room model was built to perform vibration transmission and underwater radiated noise tests. Then, the results predicted by Statistical Energy Analysis were compared with those from experiments. The comparison shows good agreement between Statistical Energy Analysis and the experimental result.
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Chen, Yan-Cheng, and 陳彥棖. "Measurement and Analysis of Vibration and Noise of Container Ship Cabin." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/e7pbbu.
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碩士國立臺灣海洋大學
系統工程暨造船學系
106
In this research, the level of noise and vibration of the engine room, steering gear room and Tally office of a 2800TEU container ship were investigated by on-site measurements which include the utilization of accelerometers, microphones and acoustic cameras. Additionally, the estimation procedure of cabin noise is established, and the results of the measurement and analysis show the same trend. First, taking the acoustic camera is used to find the locations having maximum noise, and then the accelerometers and microphones measures the signal during the different conditions. In the signal processing, the author plots the spectrogram and one third octave band by using short-time Fourier transform and time-averaging approach in order to reduce the noise effect. There are two following results found by this research: One, during stable navigation the vertical vibration frequency is same as the noise frequency, and the frequency of propeller and the largest engine excitation force and its harmonic frequency often appear in the spectrogram’s peaks in cabin noise. Another, the spectral distribution of cabin noise is mainly below 250 Hz, and the maximum sound pressure level usually happens at the center of the plate. Apart from on-site measurements, simulations of simple conditions are carried out numerically find the vertical vibration frequency of the plate is found to compare favorably with the peak frequency obtained by noise; however, there is a significant amount of deviation when comparing the amplitudes. Because of the values of noise contribution caused by the different vibration modes are different. For the whole container ship, numerically, the noise level under different excitation forces is carried out by simulating the acoustic field in the cabins; the excitation forces are available from the finite element results provided by the shipyard. The result of the analysis shows that rooms on the higher floor having the higher noise level, and also the rooms near the center of the superstructure.
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Liu, Zeng-Jir, and 柳政吉. "The Effects of High Speed Diesel Engine for Ship Vibration and Underwater Noise." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/00236805667324897471.
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碩士國立臺灣大學
造船工程學系
81
ABSTRACT The purpose of this paper is airmed to study the unbalance orces and moments of high speed disel generator and to predicthe corresponding response for ship vibration and underwateroise. In this report the developments of software on PC for analysisf unbalance moments and forces of V-type with intermediate crankrrangement of high speed disel engine is represented at first The 2nd port is using the pre & post procession of MSC/XL tostablish the F.E.M 3D+1D model for the analysis of ship naturalrequency and local frequency response by MSC/NASTRAN. In theeantime, the transfer matrix method develop in own LAB. haveeen for checking purpose and to study the boundry condition forD local analysis. Finally , with the method of MSC/NASTRAN V67 to solve under-ater noise distribution and local sound pressure level generatelyhip hull plate structure under excitation of unbalance forcesnd moments of disel generator. At last the comparision of theesults with exprimental data[6] and theoritical solution[13]ave been discussed.
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Wang, Hsin-Ta, and 王星達. "Prediction of Noise and Vibration of a FRP ship and correlations with measurements." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/87126827016320385460.
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碩士國立臺灣海洋大學
系統工程暨造船學系
92
The aim of this research is to establish the prediction model for noise and vibration of a FRP ship. Furthermore predictions and measurements were compared in order to validate the correctness between them. In vibration simulations, FEM model of a FRP ship was constructed using MSC Patran software. And the analysis was performed in two conditions, one is the ship in dry vacuum condition and the other one is the ship in wetted condition, and the added mass was calculated by using virtual mass method in MSC Nastran. Meanwhile, vibration test was conducted on a FRP patrol boat of fifteen meters in length and twenty tons in weight, which is built by LUNG TEH SHIPBUILDING CO. in SU-AO. An accelerator and spectrum analyzer were used to measure and analyse the frequency response function during the aft deck is impacted by a hammer. Input the results of measurements to ME’Scope software to attain the mode shape of the aft deck. In the aspect of noise simulations, the results of frequency response function of a FRP ship were measured and input to the SYSNOISE BEM software, and proceed to analyze the noise distributions in pilot house. Also, the noise in the pilot house was measured by sound level meter in one third octave band of the above-mentioned ship, when the ship sailing with main engine output 85﹪and rotational speed at 2000rpm. The prediction model of noise and vibration in this research has become a complete simulation process for the structure-borne vibration radiated noise. However, vibration modal test is the hardest work in this research. So only the aft deck of the ship was undergoing measurement, and proceed to compare the measurements with the predictions. Key words：FRP ship、vibration、noise、added mass、frequency response
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Lin, Li-min, and 林岦民. "The Study of Engine-Room Structural Vibration and Noise Coupling of Merchant Vessel - A Case Study of 1,800 T.E.U. Container Ship." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/hv626h.
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碩士國立臺北科技大學
製造科技研究所
103
Most of the merchant ships are designed to use two-stroke diesel engine in order to generate powerfully propulsive efficiency. The diesel engine installs in the closed engine-room space so as to producing very higher sound pressure than any other area in a ship. In this study, by the use of CATIA V5 to construct a model of a container vessel’s engine-room in accordance with the shipping company’s specification, and utilizing LMS Virtual.Lab 12 “Noise &; Vibration” simulating function to simulate the exciting effect of the vessel’s economic speed revolution. After that, by using Finite Element Method to analyze the affection of the engine-room’s structural vibration under the exciting force. In principle, the analysis of noise and vibration is based on sound pressure which is calculated by structural vibration values. In this study, the economic speed revolution of main diesel engine is 101.4 RPM and it is under 90% of maximum output power, the frequency is about 10.14 Hz, considering of this condition as the structural vibration parameters. The sound field distribution could be based on the structural mode analysis and exciting force data, then we could perform the analysis of vibro-acoustic coupling simulation. After calculating the sound pressure distribution of the engine-room, attaching different thicknesses sound-absorbing material of 25 mm, 50 mm, and 75 mm respectively on the surfaces of roof, forehead, astern, port and star sides of engine-room in order to assess the noise improvement. As the results of comparison are shown the sound pressure average values of all cases of the situation of 50 mm thick sound-absorbing material performed much better than those of 25 mm thick sound-absorbing material. The situation of 75 mm thick sound-absorbing material performs the best result, but it shows slight differences by comparing with that of 50 mm thick sound-absorbing material. We need to consider the costs of materials, construction, personnel, return of investment, and other factors in practical noise improvement plans, in other words, we must also think over the economic fundamentals.