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Numerical Prediction of the Exhaust Noise Transmission to the Interior of a Trimmed Vehicle by Using the Finite/Infinite Element Method
ISSN: 0148-7191, e-ISSN: 2688-3627
Published May 17, 2011 by SAE International in United States
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During the acceleration of a vehicle, the contribution of the exhaust noise to the interior sound pressure level is significant. The acoustic insulation brought by the trim components must be designed with that consideration in mind. As such, there is an increasing need for developing reliable methods for predicting the airborne noise transmission between the exhaust system and the sound pressure level at the passenger's ears, taking into account the positive impact of various trim components.
This paper presents a methodology that has been developed for addressing this need. Based on a finite/infinite element method, the computational procedure is divided in two steps:
- 1The first step involves the exterior acoustic field all around the vehicle. The acoustic pressure field on the exterior surface of the vehicle is computed by considering the exhaust system as acoustic source;
- 2The second step consists in computing the interior vibro-acoustic response of the vehicle by using the surface pressure from step one as excitation applied to the trimmed body finite element model.
This second step relies on a FE modal-based approach for the efficient modeling of large trimmed structures coupled to acoustic cavities. In this approach, the trim components are represented by their impedance matrices reduced to the interface degrees of freedom with the body structure and the interior acoustic cavity. These reduced impedance matrices are then projected on the structure/fluid modal bases and injected in the coupled modal system; as such the trim components are accurately taken into account when the vibro-acoustic modal model of the vehicle is solved.
The paper gives the details of the two steps of this approach as well as the key ingredients related to this original technique. Some real life validation cases (including some comparisons with measurements) are presented, proving the reliability of the method and its efficiency in an industrial automotive context.
Citationd'Udekem, D., Saitoh, M., Van den Nieuwenhof, B., and Yamamoto, T., "Numerical Prediction of the Exhaust Noise Transmission to the Interior of a Trimmed Vehicle by Using the Finite/Infinite Element Method," SAE Technical Paper 2011-01-1710, 2011, https://doi.org/10.4271/2011-01-1710.
- Free Field Technologies, ACTRAN 11 User's Manual, 2010;
- Astley, R.J. and Coyette, J.-P.. Conditioning of infinite element schemes for wave problems. Intern. J. Numerical Methods in Engineering, 17:31-41, 2001;
- Astley, R.J. and Coyette, J.-P.. The performance of spheroidal infinite elements. Intern. J. Numerical Methods in Engineering, 52:1379-1396, 2001;
- Biot, M.A. Theory of propagation of elastic waves in a fluid-saturated porous solid. i. low-frequency range. Journal of the Acoustical Society of America, 28(2): 168-178, 1956.
- Biot, M.A. Theory of propagation of elastic waves in a fluid-saturated porous solid. i. higher-frequency range. Journal of the Acoustical Society of America, 28(2):179-191, 1956.
- Biot, M.A. Mechanics of deformation and acoustic propagation in porous media. Journal of the Acoustical Society of America, 33(4):1482-1498, 1962.
- Allard, J.-F.. Propagation of sound in porous media. Elsevier Applied Science, page 1939, 1993;
- Van den Nieuwenhof, B., Lielens, G., Coyette, J.P., Acher, F., d'Udekem, D., Efficient analysis of large trimmed configurations using modal approaches, ISMA conference in Leuven, 2008.