Keywords: acoustic transmission loss, statistical energy analysis, boundary element method, maglev transrapid.

Double glazing windows, consisting of two pieces of glass, were frequently used on the some high speed trains in order to reduce the interior noise of the vehicle. The acoustic transmission losses of double glazing windows usually are directly proportional to the thicknesses of glasses and the air layer between the two pieces of glass. However, the weight has to be strictly constrained while designing the double glazing windows for a maglev transrapid vehicle.

The airflow noise outside a transrapid vehicle is much higher than a normal train, since its velocity may be as high as 500km/h. In order to determine the target octave spectrum of acoustic transmission loss of the double glazing windows, both of the outer and interior noise of a transrapid vehicle running at 500km/h is experimentally investigated. The one third octave spectrum of interior noise in a passenger chamber shows that the dominative frequencies of interior noise are from 80Hz to 2000Hz, which is considered as the frequency band to increase transmission loss of the windows on a transrapid vehicle.

In order to determine the optimal parameters of windows, the acoustic transmission loss of the double glazing window is numerically analyzed, in which the indirect boundary element method is used for studying the acoustic transmission loss in lower frequency band and the statistical energy analysis method for high frequency.

The acoustic transmission loss of double glazing windows on TR08 is measured to verify the prediction methodology mentioned above. TR08 is the vehicle running on the Maglev Transrapid Pudong Line in Shanghai. The predicted transmission loss lower than 400Hz is the result of indirect boundary element method analyzing, and frequency above 1000Hz is obtained by statistical energy analysis method. The transmission loss of the frequency between 400Hz and 1000Hz is the average of BEM and SEA analysis. The comparison between prediction and measurement shows that the error of transmission loss prediction is principally less than 5 dB. The method for simulating acoustic transmission loss can be considered as verified, since the predicted data goodly agrees to the measured data.

Then, according to the weight and size condition, the glass thicknesses, vacant space and gas are optimally determined. Based on comparing some different double glazing windows, an optimal design is finally obtained, which transmission loss increases 6~8dB than original design but keep the same weight.

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