The Experimental Study Of Composite Cavity Structure Test Samples Dimension On Sound Insulation Property

With the economic development, population increasing, international communication increasingly frequent, tourist industry more and more flourish, the high speed railway transport system plays an important role in people travel for there comfort and convenience,. So improve the running speed of trains become the inevitable tendency of development, but the speed increase will bring the noise problems, the noise may produce varying degrees of damage on people’ physical and psychological, include fatigue and irritable and the time too long may cause headaches brain swelling symptoms and so on. Therefore, provide a quiet, peaceful and comfortable driving environment to passengers is necessary. This makes how to reduce the internal noise becomes a problem we have to focus on and resolve.The sources of interior noise include wheel-rail noise, drag noise, mechanical and electrical equipment noise. These noises eventually spread through the airborne, once solid transmission and twice solid transmission to the car. For solid noise spread, make the noise suppressed or weakening in the communication process, we need to do some researches on sound transmission materials. To prevention and control of noise we can strengthen the vibration isolation ability of system, reduce the once solid sound transmission from the floors, or improve the car body structure to reduce the noise from outside, achieve to reduce the twice solid sound transmission.This paper is according to the criterion called acoustic-buildings and building component. The third part : the laboratory measurement about building component airborne sound insulation(GB/T1988.3-2005)conduct the study on sound insulation property of composite cavity structure test samples which composed by C type keels, skin material, rock wool, glass wool cloth, screws, nuts and appropriate air layers, and we want to apply this conclusion to the car structure sound insulation of high speed train.The experimental facility is the noise and vibration measurement system products by B&K company from Denmark which contains microphones, data acquisition instrument, power amplifier, twelve surfaces no direction sound source and its software system. By measure the sound insulation of test samples with different size and different air layer thickness, then receives the datum in full frequencies and draws the acoustic curves. Analysis the test samples with same area but different air layer thickness and receive the sound insulation effects of air layer thickness, also analysis the test sample with same air layer thickness but different areas and receive the sound insulation effects of area, then combine all the sound insulation datum of different area samples to seek one area which can represent this kinds of sample’ sound insulation, this area is the biggest area to present this sample’ sound insulation. In the measurement process we also discuss the measure error which cause by sealing property.All the test samples in this study installed and measured according to the specified standards the requirements. The results show that for the same test samples, their sound insulation quantity change large in low frequency and present increasing trend gradually in middle frequency band, sound insulation quantity trend to steady state in the following high frequency band. For different test samples, with the airspace thickness increasing, the sound insulation effect is remarkable in low frequency and presents upward tendency in whole bandwidth. But sound insulation quantity does not doubled with the airspace thickness doubling, and obvious increasing effects occur when the airspace thickness increase to a certain range. For different area samples with the same thickness, the whole sound insulation remarkable of large samples is higher than that of small ones.