Influence Research Of The Scale On Sound Insulation Of The Composite Hollow Specimen In The Reverberation Chamber

With the development of train speed,stronger railway noise is generated.This not only causes pollution to the social environment,but also affects the daily life of the residents around the railway and passengers’ comfort.the main source of noise in carriage is the noise reaching the passenger compartment through the body panels.Considering the limitations of factors such as the sources of noise and the generation conditions,it is difficult to directly perform noise reduction from the sound source.Now that there is a simple and highly feasible noise reduction process,the acoustic wave propagation path is processed in a related manner to reduce its propagation efficiency,thereby achieving the purpose of noise reduction.However,increase the thickness of the body panels will increase the sound insulation,which will not only waste material,but also increase the weight of the carriage.At present,the sound insulation performance of the specimen is studied mainly by changing the material type,increasing the thickness of the material or changing the combination form of the sound insulation plate.To measure the sound insulation performance of a type of wall,it is hard to determine how large area of the tested specimen should be used.That means there is a lack of data on the effect of the area of the tested specimen on the sound insulation performance.Under the above background,this dissertation takes composite hollow specimens with different thicknesses and different areas as the tested specimen to study the influence of the area and thickness of the composite hollow specimens on the sound insulation.The relationship between sound insulation and area of tested specimen provides a reference for the selection of sound insulation specimens in the future.The main results can be summarized as:(1)At the same thickness,with the decrease of the area of the specimen,the sound insulation is reduced gradually,and the sound insulation is reduced about 6 d B when the area is reduced from 8.75 m~2 to 3.28 m~2.At this time the size of the specimen has a great influence on the sound insulation.(2)At the same area,with the increase of the thickness of the specimen,the sound insulation increases gradually.The sound insulation is increased by 0.5 d B when the thickness of the specimen increases from 100 mm to 125 mm.And the thickness of the specimen increases from 125 mm to 150 mm,the sound insulation is increased by about 2 d B.In addition,increasing the thickness can effectively avoid the occurrence of low-band resonance frequencies.(3)In different frequency bands,the amount of sound insulation varies with the area of the specimen at different frequencies.In the low frequency bands,the sound insulation is reduced gradually with the decrease of the area of specimen,when the specimen area is 6.56m2,the sound insulation reaches the minimum,after that,with the decrease of the specimen area continually,the sound insulation is increased gradually.In the middle-high frequency bands,with the decrease of the specimen area,the sound insulation is also reduced gradually,but the sound insulation reaches the minimum when the specimen area is 6.56m2.After that,with the decrease of the specimen area,the sound insulation is also increased gradually.