“Tough Gear”and “High Quality” for New X-TRAIL - 5. NV Technology to Achieve EV-Level QuietnessFig. 15 Car body frame structureFig. 16 Suspension structureFig. 17 Road noise level at a constant speed of 50 km/h on the Fig. 18 Input contribution in existing vehiclesrough surface roadThe suspension is renewed (Fig. 16), and the front suspension member, which is a soft-mounted type on the previous X-TRAIL, is now a rigid type; this contributes to the high rigidity of the vehicle body. The sound sensitivity of the suspension mounting points is improved by increasing the body rigidity to maintain a low road noise level. In addition, the road noise level is improved by 1.5 dB compared to that of the previous X-TRAIL by applying softer front suspension bush and changing rear suspension member from rigid type to soft-mounted type (Fig. 17).identified on the body panel throughout the transmission path from the powertrain to the interior components, where the input contribution is high, and countermeasures based on our design policy of efficiently applying the double-wall structure are implemented.insulation performance, local sound leaks in the sound propagation path need to be prevented and sound insulation materials that have a double wall structure with a large distance between walls need to be used to improve the performance of individual components.30For efficiently Weak points are An analysis of the existing vehicles reveals that the dash penetration and toe board contributed approximately 50% (Fig. 18). For the dash penetration part, a contribution level equal to that of the other portions is achieved by thoroughly reducing holes and gaps. For the toe board, the double-wall structure consisting of the dash panel and insulator is inherited from the existing model, and the performance is improved by 5 dB by making the insulator 157% thicker than the existing model (Fig. 19) and without adding parts or increasing the mass (B → A in Fig. 20). This contributes to a weight reduction of approximately 10 kg compared with the case where mass measures are considered instead of structural measures (C in Fig. 20).6.5 Sound insulation technologyimproving the sound
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