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In the design of an automobile, an important consideration is to minimize the amount of “boom” noise that the vehicle occupant could experience. Vehicles equipped with four cylinder engines can experience powertrain boom noise in the 40 to 200 Hz frequency range. Boom noise can also be generated by road input, and it is just as annoying. In this paper, a CAE methodology for predicting boom noise is demonstrated for a vehicle in the early design stage in which only 3-D CAD geometry exists. From the CAD geometry, a detailed finite element (FE) model is constructed. This FE model is then coupled with an acoustic model of the interior cavity. The coupled structural-acoustic model is used to predict acoustic response due to powertrain inputs. As a part of the detailed design process, various design modifications were considered and implemented in the vehicle system model. Many of these modifications proved successful at reducing the boom levels in the vehicle.

Acoustic source identification is an important issue in both early and prototype validation stages of NVH design. OEMs and suppliers need to assess the entire description of vehicle noise emission, to understand and address interior comfort and exterior radiation issues. Today, none of the existing methods allow engineers to get a quick snapshot of sources contributing to the external pressure level affecting pass-by noise emission compliance, requiring long and arduous testing projects with & without physically masked components. A new acoustic imaging technique provides an important solution. The method is based on a microphone array. Like a camera, but unlike current holographic methods, the software delivers focused, near-realtime 2D colour snapshots and movies, corresponding to the sound pressure level at the region of interest. Typically, the entire side of a vehicle can be analysed during one pass-by run.

A continuously growing demand comes from the automotive industry for optimization of materials and sound insulating product packaging inside the car, so as to propose the best acoustic performance at reduced costs. A new acoustical holography system provides part of the solution to meet such a demand. The capability of measuring the acoustic field inside a vehicle with high spatial resolution makes it an advanced tool for performing extensive studies of the acoustic transparency of car openings and interior components in various environmental conditions (acoustic chamber, on road, in wind tunnel).

Noise source identification is becoming a key issue in the dimensioning and troubleshooting steps of the design process. In the automotive industry, OEM's and suppliers need to assess the entire description of vehicle noise emission, both for interior comfort and exterior radiation concerns. The resolution of pass-by noise issues pose one of the most significant problems to vehicle designers. While many commercially available systems allow the evaluation of the overall noise emission at any speed and position during the test the task of identifying specific sources is still mainly performed using component masking. A new measurement technique has been developed using a microphone array (typically 2m × 2m with 64 transducers or more) and acoustic beamforming techniques that allows visual source identification at any point during the test. Typically, the entire side of a vehicle can be evaluated with one single measurement run.