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A subjective evaluation method for the air-borne sound insulation of vehicle body in reverberation room is developed and the correlation between the subjective preference and objective noise reduction level (NRL) is investigated in this paper. The stationary vehicle's interior noise is recorded by using a digital artificial head under a given white noise excitation in the reverberation room, which demonstrates more credible than those in traditional road test methods. The recorded noises of six different vehicles are replayed and evaluated subjectively by 22 appraisers in a sound quality room. The paired comparison scoring method is employed and the check and statistic methods for the subjective scores are introduced. The subjective preference is introduced and calculated by the statistics and normalization of the effective scores, which can indicate an overall preference ranking of all the six vehicles numerically.

This paper summarizes the attributes of automotive exhaust system and provides a guideline for exhaust system design, analysis and development. The exhaust system has various attributes including vibration, acoustics or noise, durability and thermal distribution, flow and power loss, emission, in addition to its interface with vehicle. This paper describes all these attributes and the corresponding performances, and develops criteria for each of the attributes. The paper also describes the interfaces between the exhaust system and powerplant with body structure.

This paper introduces a cumulative effort on the phenomenon of exhaust flow exited noise. The mechanisms of engine combustion noise via the exhaust system and flow excited noise are analyzed. Engine combustion noise contributes most to tailpipe noise at lower engine speed while flow excited noise dominates the tailpipe noise at high engine speed. WAVE model, a one dimension CFD and Acoustics model, is used to distinguish the engine combustion noise and flow excited noise. Both CAE and tests based results are used to draw conclusions. The influence of single system and quasi-dual system on the tailpipe noise is compared with each other. The paper analyzes the balance of different diameter pipes to achieve the desired sound at different rpm range. The evaluation balance between interior sound and tailpipe noise is described.

This paper analyzes the relation between sound pressure at tailpipe and exhaust Y-pipe structure. The length of Y-pipe influences sound order distribution that influences customers' responsiveness of sound. The equal Y-pipe remains the firing order and its harmonic contents while suppressing the half order and other whole order sounds. Various lengths of equal Y-pipe also influence the magnitude and frequency distribution of tailpipe noise. An air-to-air (induction-engine-exhaust) CAE model is built to predict tailpipe noise using up-to-date software. The real air-to-air model simulation shows that the 3rd and 6th orders are the dominating contents for equal Y-pipe exhaust system in 6-cylinder engine applications. The sound pressure of the half order contents increases with the length difference between two branches of a Y-pipe. The results are useful for exhaust Y-pipe design.

The paper analyzes the characteristics of driveline torsional vibration of a RWD vehicle and provides the control methods of transmission rattle noise caused by the system torsional resonances. A driveline dynamic model of the RWD vehicle is established by multi-body dynamic method. The natural frequencies and modal shapes are calculated for each gear position and torsional vibration responses are predicted by forced vibration analysis. The system sensitivity and DOE are analyzed based on the parameterized stiffness, inertia and damping. The 2nd and 3rd order modal results show that the transmission shaft possesses the maximum amplitudes and its corresponding modal frequencies vary with different gear position. The sensitivity analysis results show that the system torsional vibration is significantly reduced by reducing clutch stiffness, increasing propeller shaft stiffness, raising half shaft stiffness, increasing the input shaft inertia and increasing the clutch damping.

The paper describes the identification and control methods of turbocharger surge noise. Some parameters, such as temperature, flow quantity, pressure, vibration, turbocharger rpm and noise, are provided to identify surge noise. The advantages and disadvantages for each parameter are analyzed. The paper identifies that some special vehicle interior noise is contributed by turbocharger surge noise by using correlation analysis of the turbocharger inlet temperature, outlet pressure and vehicle internal noise. Spectral filtration analysis shows that the surge noise frequency components are above 1000Hz with wide frequency band. Quarter wave tuner's effective frequency range is found to be consistent with the surge noise frequency band. A panfluter-resonator which is a combination of several special quarter wave tuners is invented to diminish the wide band high frequency noise.