scholarly journals Measurement of small vessel machinery vibration induced acoustic signature levels

2019 ◽  
Vol 16 (2) ◽  
pp. 87-98 ◽  
Author(s):  
GVV Pavan Kumar ◽  
V V S Prasad ◽  
B H Nagesh
Keyword(s):  
Pressure Fluctuations ◽  
Response Spectra ◽  
Underwater Sound ◽  
Underwater Noise ◽  
Noise Levels ◽  
Small Vessels ◽  
Performance Point ◽  
Engine Room ◽  
Airborne Noise ◽  
Main Engine

Ship vibrations, airborne and underwater noise levels have always been a challenging topic from a performance point of view in ship design, building and operation. The measurement shall help in monitoring the self-noise and the technical state of their machinery mechanism. The vibration levels on the main engine and auxiliary Genset foundation, airborne noise levels of the engine room and underwater self-noise levels of a small mechanized fishing trawler was measured at the jetty in idling condition.  The vibration levels on the foundation measured the average value of 0.207 mm/s for the main engine and 1.36 mm/s for auxiliary Genset. The airborne noise levels measured 99 dB (A) in the engine room. The peak underwater sound pressure levels measured 162 dB re 1µPa. The response spectra indicate the peak vibration and noise levels in the lower frequency region <1.2 kHz. The machinery excitation forces transferred to the hull surface as pressure fluctuations which generated the airborne and underwater noise levels. Though the measurement limited to jetty conditions, detailed analysis can be useful for detection, classification, and tracking of small vessels.

The Reduction of Gear Pump Pressure Ripple

1987 ◽  
Vol 201 (2) ◽  
pp. 99-106 ◽  
Author(s):  
K A Edge ◽  
B R Lipscombe
Keyword(s):  
Hydraulic System ◽  
Pressure Fluctuations ◽  
Gear Pump ◽  
Noise Levels ◽  
Flow Ripple ◽  
Flow Fluctuation ◽  
Accurate Knowledge ◽  
Airborne Noise ◽  
Pressure Ripple ◽  
Pump Pressure

Pressure fluctuations in a hydraulic system may be substantially reduced by cancelling the flow ripple produced by the pump. This paper describes a secondary flow ripple generating mechanism which introduces an equal and opposite flow fluctuation to that generated by the pump. Tests have shown that the mechanism can virtually cancel four harmonics of pressure ripple but success is dependent on an accurate knowledge of the pump flow fluctuation characteristic. This is best determined experimentally. Similar improvements can be achieved using a mechanism in a motor. This has the additional benefit of reducing torque fluctuations. The reduction in gear pump pressure ripple achieved with the mechanism has been shown to reduce overall airborne noise levels from a hydraulic system by as much as 10 dB, although the airborne noise radiated from the pump casing was not affected.

scholarly journals DEVELOPMENT OF THE AUTONOMOUS UNDERWATER NOISE RECORDER

2020 ◽  
Author(s):  
Donatas Bagočius ◽  
Aleksas Narščius
Keyword(s):  
Sound Recording ◽  
Underwater Sound ◽  
Underwater Noise ◽  
Noise Levels ◽  
Physical Energy ◽  
European Standards ◽  
Cost Efficient ◽  
The Cost

An underwater noise is the most pervasive type of physical energy that spreads in underwater marine environment. The concerns regarding man-made underwater noise effects on the aquatic animals became prominent within scientific communities. The determination of underwater noise levels became very actual either for environmental monitoring or scientific research purposes. Various tools for acquisition of the underwater sound as well, modelling became available, although some techniques are costly and requires special considerations. One of the examples are the sound recording devices containing hydrophones along with digital sound acquisition systems used for recording of ambient (continuous) underwater sounds. By the date there are already developed the international and European standards for monitoring the long term (yearly) underwater continuous noise levels. However, the techniques known to be able to record the short and mid-term noise levels can serve for the research purposes greatly. In this research the cost efficient autonomous underwater sound recorder was developed, with the purpose to record an ambient underwater noise continuously and autonomously for the periods of up to 15 days, following the already known methods. In this paper we present the steps of the development of the autonomous recorder, its features and capabilities as well, calibration results of the underwater sound recording system.

scholarly journals Measurement of Underwater Acoustic Energy Radiated by Single Raindrops

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2687
Author(s):  
Shu Liu ◽  
Qi Li ◽  
Dajing Shang ◽  
Rui Tang ◽  
Qingming Zhang
Keyword(s):  
Ambient Noise ◽  
Sound Pressure ◽  
Tap Water ◽  
Acoustic Energy ◽  
Underwater Sound ◽  
Underwater Noise ◽  
Energy Characteristics ◽  
Sound Energy ◽  
Dipole Radiation ◽  
Series Of Experiments

Underwater noise produced by rainfall is an important component of underwater ambient noise. For example, the existence of rainfall noise causes strong disturbances to sonar performance. The underwater noise produced by a single raindrop is the basis of rainfall noise. Therefore, it is necessary to study the associated underwater noise when drops strike the water surface. Previous research focused primarily on the sound pressure and frequency spectrum of underwater noise from single raindrops, but the study on its sound energy is insufficient. The purpose of this paper is to propose a method for predicting the acoustic energy generated by raindrops of any diameter. Here, a formula was derived to calculate the underwater sound energy radiated by single raindrops based on a dipole radiation pattern. A series of experiments were conducted to measure the underwater sound energy in a 15 m × 9 m × 6 m reverberation tank filled with tap water. The analysis of the acoustic energy characteristics and conversion efficiency from kinetic to acoustic energy helped develop the model to predict the average underwater sound energy radiated by single raindrops. Using this model, the total underwater sound energy of all raindrops during a rainfall event can be predicted based on the drop size distribution.

The Quantification of Internal Noise Levels and Wall Pressure Spectra in Industrial Gas Pipelines

1991 ◽  
Author(s):  
M. P. Norton ◽  
A. Pruiti
Keyword(s):  
Prediction Models ◽  
Transmission Loss ◽  
Pressure Fluctuations ◽  
Internal Noise ◽  
Wall Pressure ◽  
Gas Pipelines ◽  
Noise Levels ◽  
Empirical Prediction ◽  
Wall Pressure Fluctuations ◽  
Semi Empirical

Abstract This paper addresses the issue of quantifying the internal noise levels/wall pressure fluctuations in industrial gas pipelines. This quantification of internal noise levels/wall pressure fluctuations allows for external noise radiation from pipelines to be specified in absolute levels via appropriate noise prediction models. Semi-empirical prediction models based upon (i) estimated vibration levels and radiation ratios, (ii) semi-empirical transmission loss models, and (iii) statistical energy analysis models have already been reported on by Norton and Pruiti 1,3 and are not reported on here.

Lessons from Emma Maersk Flooding – February 2013

2015 ◽  
Author(s):  
Chilukuri Maheshwar
Keyword(s):  
Lessons Learned ◽  
Suez Canal ◽  
Container Ship ◽  
Engine Room ◽  
Mechanical Breakdown ◽  
Engine Cylinder ◽  
The Cost ◽  
Main Engine

In February 2013, in the 2005 built 15500 TEU 397m long container ship EMMA MÆRSK a severe leakage occurred in as it was passing southbound through the Suez Canal. The leakage occurred due to mechanical breakdown of a stern thruster causing flooding of the shaft tunnel and filling up the engine room with 14000 m³ of seawater within a span of two hours, submerging the main engine cylinder heads-level equal to the outside water draft of 15.1 m. The cost of repairs and loss of revenue for six months amounted to a few million dollars. This paper highlights some of the lessons learned from this incident.

APPLICATION OF FUZZY ANALYTIC HIERARCHY PROSES FOR ERROR DETECTION OF AUXILARY SYSTEMS OF SHIP MAIN DIESEL ENGINES

2021 ◽  
Vol 157 (A2) ◽  
Author(s):  
H Demirel ◽  
K Ünlügençoğlu ◽  
F Alarçin ◽  
A Balin
Keyword(s):  
Diesel Engine ◽  
Error Detection ◽  
Cooling System ◽  
Detection System ◽  
Analytic Hierarchy ◽  
Engine Room ◽  
Air Supply ◽  
Solution Methods ◽  
Marine Engineering ◽  
Main Engine

Ship engine room has a structure which has to meet a number of needs with regard to administrative conditions. Therefore, when the complicated structure of engine room are considered, even a simple mechanical failure, if no measures taken abruptly, grows into irreversible condition, causing losses that cannot be compensated. A well-qualified ship engine conductor along with an effective error detection system is needed to detect failure and act immediately against any engine impairments possible. This study aims to manage troubleshooting in main engine auxiliary systems which cover cooling, lubricating and cooling oil and fuel systems. The study is also thought to be a good reference for maintenance processes for marine engineering operators. Breakdown of main engine equipment are examined and troubles hooting program is developed for using Fuzzy Analytic Hierarchy Process (F-AHP) determine solution methods and causes of such breakdowns. In this paper, a fuzzy Multi Criteria Decision Making (MCDM) methodology was proposed to determine the most effected system of the ship main diesel engine. The results showed that fuel system was the most effected alternative, as being followed subsequently by cooling system, governor system, air supply system and oiling system. The results were based upon the opinions of three experts groups who ranked the ship main diesel engine systems alternatives according to twenty-nine criteria expert selected.

Noise Control Decision Process for Marine Vessels

2014 ◽  
Author(s):  
Raymond W. Fischer ◽  
Louis M. Pettit
Keyword(s):  
Marine Mammals ◽  
Noise Control ◽  
Regulatory Body ◽  
Noise Levels ◽  
Radiated Noise ◽  
Underwater Radiated Noise ◽  
Sound Levels ◽  
Airborne Noise ◽  
Control Decision ◽  
Marine Vessels

There is a price to be paid to achieve compliance with the acoustic requirements imposed by regulatory agencies. Acoustic requirements typically appear in ship specifications as airborne and/or underwater radiated noise limits as the need to preclude hearing loss for crew members and the need to control sound levels experienced by marine mammals receive more recognition. Recent changes and additions to regulatory body requirements addressing compartment airborne noise and underwater radiated noise can be found in IMO Resolution MSC.337(91) Annex 1 and Annex 2 which state that IMO Resolution A.468(XII) “Code on Noise Levels Onboard Ships” shall take effect on 1 July 2014 for all SOLAS compliant vessels. Thus the airborne noise levels in compartments and at on-deck work stations onboard as-built ships seeking a SOLAS certificate will need to be measured, and must demonstrate compliance with noise limits stated in paragraph 4.2 of IMO Resolution A.468(XII). IMO “Guidelines for the Reduction of Underwater Noise from Commercial Shipping to Address Adverse Impacts on Marine Life” dated 7 April 2014 and agencies such as ICES and DNV have established guidance and/or criteria for control of underwater radiated noise from vessels, and these too are now commonly appearing in ship specifications. Specifications referencing such criteria typically require that compliance be demonstrated by at-sea testing of underwater radiated noise. Making the correct decisions during the ship design process will minimize costs for noise control and will provide a positive return on investment. The process of how best to comply with noise limits while minimizing costs through optimization of noise control treatments and design approaches is discussed.

A Fuzzy DEMATAL Model Proposal for the Cause and Effect of the Fault Occuring in the Auxiliary Systems of the Ships' Main Engine

2018 ◽  
Vol Vol 160 (A2) ◽  
Author(s):  
A Balin ◽  
H Demirel ◽  
E Celik ◽  
F Alarcin
Keyword(s):  
Decision Making ◽  
Error Detection ◽  
Detection System ◽  
Causal Effect ◽  
Complex Structure ◽  
Fuel Oil ◽  
Fuzzy Dematel ◽  
Engine Room ◽  
Engine Failure ◽  
Main Engine

The ship engine room has a structure that meets a number of needs related to administrative conditions. Even if a simple mechanical error is considered to be the addition of human errors into the complex structure of the engine room, it can lead to undetected loss. How the causes and effects of the detected faults affect the system is as important as an effective fault detection system to detect the fault and take immediate action against any possible engine failure. This study reveals the causes of problems occurring in the main engine auxiliary systems including cooling, lubricating, cooling oil and fuel systems, and the extent of these problems affecting the system. While the Decision Making Trial and Evaluation Laboratory supports to identify and analyze the error detection of auxiliary systems with respect to causal effect relation diagram, fuzzy sets deal with the uncertainty in decision-making and human judgements through the DEMATEL. Therefore, fuzzy DEMATEL approach is applied to examine the causes and the weights of the faults and their relation to each other in the auxiliary systems. When we look at the result of the proposed approach, fuel oil pump failures has more impact on the all system and air cooler problems has the second highest place among the all errors.

Methodology for environmental impact assessment of underwater noise on marine mammals

2011 ◽  
Vol 51 (1) ◽  
pp. 467
Author(s):  
Dick Petersen ◽  
Antoine David ◽  
Darren Jurevicius
Keyword(s):  
Oil And Gas ◽  
Sound Propagation ◽  
Underwater Acoustics ◽  
Oil And Gas Industry ◽  
Marine Species ◽  
Marine Ecology ◽  
Underwater Sound ◽  
Underwater Noise ◽  
Mammal Species ◽  
Marine Fauna

The oil and gas industry uses some exploration and production technologies that produce high levels of underwater sound, such as seismic surveys, underwater blasting for demolition and construction, and offshore piling. These underwater noise sources have the potential to impact marine species, which are usually reliant on sound instead of light as their primary sense for communication and sensing their environment. Regulatory interest in minimising the impacts of underwater noise on marine fauna is increasing. This paper presents a methodology for assessing these environmental impacts, with particular focus on cetaceans (whales and dolphins) and pinnipeds (seals and sea lions), although it can easily be adapted to other marine mammal species and fishes. It requires input from a variety of fields, such as: underwater acoustics for sound propagation modelling and source noise characterisation; marine bio-acoustics for determining the effects of sound on marine species’ hearing and communication; and marine ecology for identifying the marine species that may be affected and assessing the biological importance of noise-affected marine areas. These inputs are used in a risk assessment to assess the likely impacts of underwater noise on marine species, which is a collaborative effort by specialists in the fields of underwater acoustics, marine bio-acoustics and marine ecology.

Detection of long term trends in underwater noise levels

2016 ◽  
Vol 140 (4) ◽  
pp. 3024-3024
Author(s):  
Claire F. Powell ◽  
Nathan D. Merchant
Keyword(s):  
Underwater Noise ◽  
Noise Levels ◽  
Long Term Trends
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