Study On Car-passenger Ferry Cabin Noise Prediction And Control

The cabin noise is an important criterion in high-performance ships,the noise prediction is the premise of the ship noise control and low noise design.Shipbuilding techniques of China is able to meet the noise standard of IMO in 1981,However,in order to fulfill the newly revised cabin-noise standard,a series of noise control need to be researched.In this paper,the statistical energy analysis is implemented on the newly designed 100m-class carpassenger ferry,the ship cabin noise is predicted.The six-subsystem coupling model is applied to explain the power balance equation.The method to quantify the modal density,damping loss,coupling damping loss and input power is stated in detail.Refer to the CAD drawing of car-passenger ferry,the CATIA software is used to build the ship shell structure,then it is imported into the Hyper mesh to be divided into units.The finite element units are defined properties then imported into VAONE to build statistical energy plate,beam and cavity subsystem.As the SEA method is not applicable in all frequency,for the ship machinery space,the modal overlap factor is discussed to explore the SEA application scope,the FE method is used in the lower frequency,the FE – SEA method is used in medium frequency and the SEA method is used in high frequency.The load main engine,auxiliary engine,water-jet propulsion,air condition and all kinds of pumps are considered as the noise sources in the octave band.The calculation frequency is defined as the 16 ~ 8000 Hz in 1/3 octave band.The damping loss is set as the experience value 1% to predict the ship cabin noise.Putting forward a preliminary plan to satisfy the new cabin noise standard.Considering the ship interior materials and layout,noise prediction is carried out and fit well with the experience prediction to prove the feasibility of experience method and it necessary to consider the interior layout in the noise cabin prediction.To analysis the transmission mode of airborne and structure-borne noise and the main noise sources of different deck is explored.The effects of water on cabin noise is listed separately above and blow waterline.Considering factors that may impact the precision of cabin noise prediction are discussed from two aspects,i.e.the stiffened plates and ballast tank liquid.Based on the results of noise prediction,different noise reduction method is presented from local aspect,such as the acoustic enclosure calculation as the noise source protection,the application of sound-absorbing material on the noise transmission way and the effect of damping installation position,the damping layer thickness,and damping type on cabin noise.In view of the high requirement for noise as the clinic,the floating cabin is put forward as a kind of noise reduction method.As the cabin noise from upper structure mainly comes from the radiated noise of air condition,designing a new kind of muffler and top ventilator to reduce the noise of air condition,let the clinic noise meet the IMO standard.Finally in the chapter a set of noise reduction method is summarized.