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Problem StatementThe main engines of Stena Britannica and Stena Hollandica produce a low frequency vibration which results in complaints from inhabitants of Hoek van Holland during arrival and departure. We have done measurements by a company and that gave the following facts:· Only the 8-cylinder engines produce the low frequency· The frequency is appr 10 Hz· The longer the maneuver takes (bad weather) the higher the number of complaints.· The effect is vibrations on the houses and in particular the windows.· It causes also pressure on the ears.· The houses effected are more or less perpendicular (right angle) on the funnel of the vessel.· The cause of the vibration is the combined effect of the engine exhaust and the funnel· A possible solution, brought forward by the investigating company was to use a so called “? lambda damper”. This however is quite a large installation.. What I would like to know if there are technical solutions to take away or reduce the low frequency effect to the housing of Hoek van Holland. Preferably as easy and simple and cheap as possible. If not at all available, the confirmation to eventually go for the “? lambda damper” as only solution, would be helpful as well!Executive SummaryMost of the commercial activity observed in the field of noise control reflects optimization of engine mounts and silencer design. The Chinese are most active in the patent literature for marine engine noise control (see WO2018133558A1 below, rough English translation available). General Electric is also actively patenting for the jet engine applications.Two novel approaches include Active Noise Control (similar to noise canceling headphones) and Carbon Nanotube technologies. Active Noise Control is commercially available (MTU/Rolls Royce), while Carbon Nanotubes are still at the R&D stage.A combination of acoustic sound analysis (to pinpoint the most important sources of the 10Hz vibration) and finite element analysis may be beneficial to assess the likelihood that a “1/4 lambda damper” (or other proposed solutions) would be successful before making a costly capital investment.Key Search Words from Problem StatementQuarter Wavelength RuleNoise controlMarine diesel engine noise reductionActive noise reductionSearch ResultsArticle TitleAbstract Hot LinksThe Quarter Wavelength Rule And Why It’s Important To YouThere is a rule that acoustical engineers follow in creating sound absorbing technologies. It is called the quarter wavelength rule. Without getting too technical, you can define the rule in its impact upon a lower frequency wavelength. Lets use 30 Hz. as our wavelength in this example. A 30 Hz. wave is approximately 37′ long. In order to absorb this long wavelength, we need to create a sound absorbing device that can absorb completely, at least 25% of this wavelength. That would be a distance of a little over 9′. of Noise Emissions from Diesel Engine SurfacesOne of the effects of the existing and proposed European legislation limiting vehicle noise has been to generate a requirement for quieter engines. A simple analysis of the vibration of the external surfaces of several in-line engine structures has shown how the noise from the engine surfaces can be reduced, provided that all the thin-section areas of the external surface are treated.Noise-reduction techniques have been evolved for all the commonly used surface structures for diesel engines, and these are described in this paper. Four in-line diesel engines have been treated by these techniques, and noise reductions of 5-8 dBA have been obtained. In all cases, the same manufacturing plant was used to machine the modified crankcase/cylinder block casting; the valve gear cover and sump were modified versions of those already fitted to the engine. controlAn effective model for noise control is the source, path, and receiver model by Bolt and Ingard.[8]?Hazardous noise can be controlled by reducing the noise output at its source, minimizing the noise as it travels along a path to the listener, and providing equipment to the listener or receiver to attenuate the noise. Quieting engine noiseActive noise reductionIn addition to the passive sound reduction techniques listed above, MTU, the manufacturer of large diesel engines, is working to bring active noise reduction technology to the marine world. MTU is now testing active vibration engine mounts for use on its 2000 and 4000 series engines. The operating principal of the MTU system parallels that used in noise canceling headphones. Interfering noise is sampled, amplified and phase inverted to produce an “anti-noise” within the headphone’s earcup that will ideally cancel the unwanted noise.? Carbon Nanotubes Shush Loud Heating and Air Conditioning SystemsWithout the need for fibrous materials acting as sound absorbers—materials that break down over time and can enter the air ducts—the new technology can be used by hospitals, where conventional silencers can pose a threat to patients. They can control low frequency noise while taking up 90 percent less space. They can also adapt to changing sound sources, which conventional silencers can’t. The new technology will be valuable not only to hospitals, but to schools and residents in industrial areas as well. noises. Raising comfort.Significant noise reduction can be achieved with our standardized advanced mounting systems. Generally speaking, all yacht engines are elastically mounted. Typical configurations are:— Flange mounted gearbox, resilient mounts — Freestanding gearbox; resilient mounts— Standard acoustic optimized coupling systems The Active Noise Control (ANC) system contains actuators andsensors to identify disturbing frequencies and allows to reduce them to an absolute minimum to reach the maximum comfort and quietness on board. The system is flexible and powerful enough to optimize and calibrate it to the special ship characteristics to reach the optimum result. It is also able to improve and fine tune the acoustic behaviour of existing installations on board.With the double elastic mounts, the soundproof engine sits on a frame that is also elastic-mounted. This leads to significantly less structure-borne noise being passed into the ship’s structure as it is the case with single elastic mounts.Integrating the entire engine into a sound-reducing capsule also reduces airborne noises to a minimum which results in maximum comfort and less insulation effort of the machine room. Ideal Tool for Your Acoustic Measurement NeedsHolography measurement solutions have become the globally recognized standard for sound analysis measurement. But that’s hardly surprising, since the extensive range of products offers you solutions to virtually any sound localization issue in research, development, production and long-term monitoring. Whether they’re used for localizing sound sources in aeroacoustic wind tunnels, studying interactions in the animal kingdom, or to monitor the health of your equipment, beamforming and holography measurement equipment provide an easy solution to your problem. investigation of a diesel engine power, torque and noise emission using water–diesel emulsionsHighlightsThe 2% water–diesel blend showed the highest engine power and torque.There are not significant differences between noise emissions of neat diesel and E2.Lower peak HRR at higher engine speed led to weaker and more silent combustion for emulsions than neat diesel.Thermal efficiency increase from 25% to 75% engine load may lead to more powerful and louder combustion.Engine noise reduction from 75% to 100% load may be due to the effect of ignition delay decrement. and experimental verification of a robust active noise control system for a diesel engine in submarinesThis paper presents the development and experimental validation of an ANC (active noise control)-system designed for a particular application in the exhaust line of a submarine. Thereby, tonal components of the exhaust noise in the frequency band from 75 Hz to 120 Hz are reduced by more than 30 dB. The ANC-system is based on the feedforward leaky FxLMS-algorithm. The observability of the sound pressure in standing wave field is ensured by using two error microphones. The noninvasive online plant identification method is used to increase the robustness of the controller. Online plant identification is extended by a time-varying convergence gain to improve the performance in the presence of slight error in the frequency of the reference signal. Active noise control of a diesel generator in a luxury yachtActive noise control has been applied to a variety of systems in order to improve performance without the increases in size and weight that would otherwise be required by traditional passive noise control treatments. This paper investigates the application of an active noise control system to the control of generator noise in the master cabin of a luxury yacht. A multichannel, multi-tonal active noise control system employing loudspeakers and microphones in the master cabin of the yacht is investigated. It is shown that, due to the high number of engine orders produced by the generator, in order to achieve significantly perceptible levels of noise attenuation it is necessary to control at least 7 individual orders. A controller is investigated which targets 19 engine orders and it is shown to achieve in excess of 5 dB broadband attenuation, whilst achieving up to 23 dB attenuation in individual orders. This corresponds to a 23% reduction in the Zwicker loudness. Hybrid approach to noise control of industrial exhaust systemsThis study aims to present a procedure for optimal design of hybrid noise control systems for exhaust ducts from large fans and high radiated sound power, in an industrial environment. Reactive, resistive or hybrid silencers are considered as alternatives with the possibility of adding a supplementary active noise control system to mitigate remaining noise of multiple low frequencies, which are difficult to be attenuated by passive means.Algorithms are proposed for the implementation of optimal hybrid passive/active design and the main theoretical and practical fundamentals involved are showed.Two effective solutions for a real industrial exhaust system are presented as examples of applications of hybrid optimal design procedure proposed. The first one uses of Helmholtz resonators (to attenuate lower frequencies) and resistive silencer parallel lamellae (to lower the midrange and high frequencies). The second one adopts resistive silencer of parallel lamellae and a forward active noise control system.This is a hybrid approach that is not treated in this manner in the available literature, especially in the text books of applied acoustics engineering. Classification of Noise Reduction SilencersReflective or Reactive silencersThe primary function of a reactive silencer is to reflect sound waves back to the source. Energy is dissipated in the extended flow path resulting from internal reflections and by absorption at the source. The operation principle of the reactive silencers is a combination of lambda/4- and Helmholtz-resonators acting as acoustic filters. Reactive silencers have tuned cavities or membranes and are designed to attenuate low frequency noise from machines.The reactive silencer may have excellent low frequency performance, is non-fibrous and cleanable and has small or negligible pressure loss. The simplest kind of a reactive muffler is the expansion chamber. In general reactive silencers are used for fixed speed machinery producing pure tones. The reactive silencer is suitable for engines requiring very low exhaust system back pressures for a maximum engine performance. Design Analysis and Performance Evaluation of Reactive Silencer by SYSNOISENoise pollution created by engines becomes a vital concern when concern used in residential areas or area where noise creates hazard. Issues concerning the design and use of large-scale silencers are more prevalent today than ever before. The main sources of noise in an engine are the exhaust noise and the noise produced due to friction of various parts of the engine. The exhaust noise is the most dominant. With the increased use of large industrial machinery and the increase in public awareness and concern for noise control, the desire to be able to able to properly design silencer for specific application is increasing. Due to the size and expense of silencers, it would be beneficial to have means to predict the insertion loss (IL) or transmission loss (TL) characteristics at the design stage. To properly accomplish this, many factors such as geometry, flow effects, break out noise, and self generated noise must be considered. There are a number of methods currently used to model and investigates the acoustic performance (TL) of mufflers including analytical methods such as the TMM, computational methods including the use of FEM & BEM & experimental measurement techniques .The use of finite element method (FEM) & the boundary element method (BEM) can aid in the prediction & design. Noise integrated treatment device and method for marine diesel engineThe invention discloses a noise integrated treatment device and method for a marine diesel engine. The device is composed of a mounting support and an integrated set connected thereto. According to the invention, active noise reduction and noise-employing power generation are combined for noise integrated treatment and noise field of the marine diesel engine is converted to dynamic ultrasonogram by utilizing acoustic imaging technology. By adopting the device and method provided by the invention, influence on dynamic mechanical structure by low frequency noise can be reduced substantially and automatic treatment of marine diesel engine noise is 107146600A To note, there is a tremendous amount of patent activity in China in this areaVibration damping and noise reduction device and marine diesel engine propulsion power module systemA vibration damping and noise reduction device and a marine diesel engine propulsion power module system, wherein the power module comprises: a diesel engine (1) and a gear box (2) connected to the diesel engine (1) via a transmission connector; wherein, the vibration damping and noise reduction device can meet the requirement of a four-level classification system of vibration damping and noise reduction of the marine diesel engine propulsion power module, and wherein the vibration damping and noise reduction device comprises: a first vibration damping and noise reduction structure located on a diesel engine (1) side and a second vibration damping and noise reduction structure located on a gear box (2) side. The device can provide a standardized and serialized diesel propulsion power module for marine power design, so as to meet a rapid and precise design goal of the marine diesel engine propulsion power module.WO2018133558A1(Chinese language)(for English translation) ................
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