A Case Study on Clean Side Duct Radiated Shell Noise Prediction

Paper #:
  • 2017-01-0444

  • 2017-03-28
Engine air induction shell noise is a structure borne noise that radiates from the surface of the air induction system. The noise is driven by pulsating engine induction air and is perceived as annoying by vehicle passengers. The problem is aggravated by vehicle design demands for low weight components packaged in an increasingly tight under hood environment. Shell noise problems are often not discovered until production intent parts are available and tested on the vehicle. Part changes are often necessary which threatens program timing. Shell noise can negate air induction NVH development by overriding acoustic abatement features such as Helmholtz resonators and large air boxes. Shell noise should be analyzed in the air induction system design phase and a good shell noise analytical process and targets must be defined. A numerical analytical process is developed to predict the radiated sound power of air induction components. First, internal pressure of the component is used to drive a frequency response finite element model with a finite element program called GENESIS. Then, two methods are utilized to predict the radiated sound power. One method is using GENESIS to estimate radiated sound power using the Rayleigh-Method. The other method is that resulting surface velocities are applied to a boundary element model (BEM) and radiated sound power is predicted. Several air induction clean side ducts are selected for this study. The ducts shell noise is assessed in terms of material strength and structural stiffness. Noise levels are measured at the driver’s ear and inside of the clean side ducts. Measured noise levels drive a speaker and sound intensity measurements are made on a bench. Results of the bench study are compared with the prediction data from the developed numerical analytical process. Results of the correlation conclude that the numerical process is good for predicting radiated sound power of engine air induction components. The boundary element mode has better correlation than Rayleigh Integral. It was also determined that Rayleigh Integral was reasonably accurate and efficiently good for comparing the similar designs of clean side ducts.
Also in:
  • SAE International Journal of Vehicle Dynamics, Stability, and NVH - V126-10
  • SAE International Journal of Vehicle Dynamics, Stability, and NVH - V126-10EJ
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