Research On Sound Insulation Performance Of Power Cabin Cover For Construction Machinery Based On Band Gap Theory

Ventilation,heat dispersion and noise isolation are contradictory in power cabin cover design for construction machinery.For one hand,heat dispersion requires enough openings on the power cabin cover;for another hand,big openings may lead leakage of the radiated noise of the engine and reverberation noise in the power cabin cover,and it may cause serious noise pollution.Thus,in the research on NVH performance of construction machinery,it’s urgent to design reasonable structure of the power cabin cover to satisfy the requirements of noise reduction round the premise that the heat emission efficiency is big enough.In this thesis,some tandem vibratory roller is selected as the object to study.For the balance of heat dispersion and noise reduction,band gap theory for periodic structure is applied to design a double-layer periodic structure of the power cabin cover.Based on the noise characteristics of the tandem vibratory roller,the acoustic transmission loss of the power cabin cover is improved.The improvement of the improved structure is verified by the test in reverberation-anechoic chamber and the field test.The details of this thesis are as follows:Firstly,the finite element model of the unit cell is established,and the band gap characteristic of the unit cell is analysed.The finite element model of the ventilation structure on the power cabin cover is established by assembling the finite element model of the unit cell,and its transmission loss is calculated.The parametric study on the main parameters of the unit cell is conducted to identify the relationships between those parameters and its transmission loss.And then,acoustic imaging technology is used to identify the characteristics of the noisy caused by the tandem vibratory roller so that two goal frequency bands in which the power cabin cover has bad sound insulation performance are identified.Based on the relationships between the parameters and the transmission loss,the improved structure is determined,and its transmission loss is also computed.After that,the transmission loss of the improved structure and a plate with the same ventilation areas are tested by reverberation-anechoic chamber method to verify the improvement on sound insulation performance.The noise level of the tandem vibratory roller is tested in the field before and after assembling the improver structure.The result of this thesis shows that the designed double-layer periodic structure of the power cabin cover with the same ventilation areas has good sound insulation performance.In those two frequency bands(518-672 Hz,915-1085Hz),the transmission loss of the improved structure is respectively improved to 16.0d B and 19.1d B(increased by 33% and 59%compared to the plate with same ventilation areas).In the field test,the sound pressure level near the ventilation structure on the left side is respectively decreased by 4.3d B(A)and 4.1d B(A).The research on sound insulation performance of power cabin cover for the roller based on band gap theory in this thesis establishes an approach for sound isolation structure design considering the balance of heat dispersion and noise reduction,and it can provide theoretical guide and technology support for noise reduction design on other construction machineries.