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Vehicle Vibro-Acoustic Response Computation and Control

Elwali, Wael

Abstract Details

2013, PhD, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Vehicle interior noise is generally caused by a variety of mechanical sources, such as engine, road, intake, exhaust and aerodynamic excitations, which may be transmitted into the passenger compartment via structure-borne or air-borne paths. Many of these responses occur at relatively low frequencies that are mostly below 600Hz. At this frequency range, the dominant path is often structure-borne type. The underlying physics governing this type of dynamic behavior can be represented by the acoustic frequency response function (AFRF). Hence, understanding the factors influencing AFRF and the ability to quantify the function accurately is desirable in analyzing, designing and refining the vibro-acoustic behavior of motor vehicle interior. The analytical-numerical technique, based on structure-fluid modal coupling formulation and modal superposition method, is a faster computational tool than the finite element and boundary element methods. However, the need for analytical representations of cavity modes limits this technique to simple shapes such as rectangular cavities in application to vehicle interior NVH (noise, vibration and harshness) problems. To overcome this limitation, a combined analytical-finite element approach is developed for more accurate representation and time efficient calculation of AFRFs of a 3-dimensional vehicle cavity with planar irregularities. Results show that the proposed approach out-performs the direct finite element method in terms of computational time efficiency. Moreover, the AFRF obtained using the direct finite element method with finer mesh converges to that predicted by the combined analytical-finite element approach. It can also be seen that the simple rectangular cavity approximation is sufficient to give an order of magnitude response and roughly describe the general trend of AFRF. However, the need of irregular cavity AFRF becomes necessary when the response location and phase are important in case of noise control applications. In terms of actively controlling vehicle interior noise within 0-600 Hz range, active structural acoustic control (ASAC) technique is numerically studied for its ability to reduce vehicle interior noise and improve speech intelligibility and NVH characteristics of the vehicle. ASAC applies active forces to the structure causing vibrations and through vibro-acoustic coupling, these vibrations radiate noise counteracting the primary noise inside the compartment. This technique becomes another alternative to the popular active noise control (ANC) where it can perform better especially for controlling sound from vibrating structures. Results also show that applied forces based on partial area control have more potential in reducing noise within the region of interest than those based on global area control. Moreover, it is found that when ASAC is applied at the same panel radiating the primary noise, a significant reduction in the total acoustic potential energy in the region of interest is achieved. It was also observed that the performance of ASAC improves more as the number of control forces is increased. However, when ASAC is applied at a panel different from the primary noise radiating panel, ASAC becomes ineffective. Moreover, results indicate that, in this case, increasing the number of control forces does not improve the total acoustic potential energy reduction in the region of interest.
Teik Lim, Ph.D. (Committee Chair)
J. Kim, Ph.D. (Committee Member)
David Thompson, Ph.D. (Committee Member)
Kumar Vemaganti, Ph.D. (Committee Member)
146 p.

Recommended Citations

Citations

  • Elwali, W. (2013). Vehicle Vibro-Acoustic Response Computation and Control [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382373197

    APA Style (7th edition)

  • Elwali, Wael. Vehicle Vibro-Acoustic Response Computation and Control. 2013. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382373197.

    MLA Style (8th edition)

  • Elwali, Wael. "Vehicle Vibro-Acoustic Response Computation and Control." Doctoral dissertation, University of Cincinnati, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382373197

    Chicago Manual of Style (17th edition)