Isolation Performance Of An Enclosure With Apertures

Diesel locomotive is widely used due to its good adaptability and low demand for railway lines.But noise radiated by an internal combustion engine is very high.As people pay more and more attention to the noise problem of locomotives,it is possible to consider using a sound insulation cover on a certain type of diesel locomotive to cover it to reduce the sound radiation along the line.When ventilation for heat removal is required,noise transmit from the ventilation,and the isolation performance of the enclosure reduces.In this paper by the simulations an enclosure with apertures was analyzed.Firstly,using the theory of composite partition walls,the effect of the size of the sound insulation of the wall and the ratio of different opening areas on the overall sound insulation when the sound insulation cover is opened is calculated;the numerical simulation is used to calculate the opening area ratios of 1%,2% and 3% The sound insulation capacity of the sound insulation cover is analyzed,and the sound insulation capacity of the rigid and 3mm thick steel plate sound insulation cover is analyzed when the opening area ratio is 3%.Secondly,through numerical simulation,the sound insulation of the three opening shapes of circle,square and slit and the sound insulation of the sound insulation cover when the slit is in six typical positions are calculated,and the total sound pressure level and the total sound pressure level at the six opening positions are calculated.The sound pressure levels of direct sound and reverberation sound are analyzed,and the reasons for the different sound insulation levels when the slits are located at different positions are analyzed.Finally,the experiment selected Nano sponge as a sound-absorbing material to add to the inner wall of the sound insulation cover.Through simulation calculation,the sound insulation volume of the sound insulation cover before and after the sound-absorbing material was added,and the sound pressure level at the opening were compared and analyzed.The conclusions are as follows:When the sound insulation cover is open,as the sound insulation of the wall increases,the sound insulation of the sound insulation cover has a maximum value;when the sound insulation cover wall is rigid or 3mm thick steel plate,its average sound insulation in the frequency band is 13.4d B and respectively The sound insulation of the sound insulation cover when the opening area ratio is 1% is 2.2d B and 3.5d B higher than when the opening area ratio is 2% and 3%,respectively.When the opening is a slit,a circle,or a square,the sound insulation is more consistent within 100～1000Hz.In the 1000Hz～3000Hz frequency band,the sound insulation is 13.8d B,15.1d B and 14.8d B,respectively.When the opening is a slit,the sound insulation The smallest.The slits are in six different positions,and the sound insulation is low at the corners of the structure and near the sound source,and the reverberation sound is dominant at each opening position.Adding Nano-sponge to the sound insulation cover increases the sound insulation by 5.5d B,the average sound pressure level in the cover is reduced by 8d B,and the average noise reduction at the opening is 8.2d B.