At present, noise quality is a crucial issue for automotive and heavy machinery manufacturers. In addition to the strict governmental regulations, it is important for automobiles to maintain the perception of quality in costumer’s mind. On the other hand, the sound of heavy machinery is a safety issue. Loud noises can make it harder for heavy machinery operators to hear. To comply with noise requirements and to maintain the sound quality inside the cabin, automotive and heavy machinery manufacturers have turned to acoustic simulations. CAE tools have been giving competitive advantages to companies for many years by shortening development time and reducing costs by allowing engineers to achieve perfect design with less prototypes. Acoustic simulation can also be used to study noise sources including powertrain, fan, intake & exhaust, and cabin noise.
For powertrain, acoustic simulation lets users learn about the contribution of different parts to the noise and vibration of the powertrain components. For example, when Renault had launched its electric car, it had to guarantee NVH requirements of new design because end-users expect electric vehicles to be very quiet. Therefore, vibration levels obtained by Nastran were input in Actran for predicting the radiating noise.
Acoustic simulation software also helps manufacturers improve intake and exhaust noise, the sources of the noise and how it radiates. For example, it helped Tenecco for its truck muffler. Simulation was used to predict the pipe and the shell noise of complex exhaust system. Acoustic and structural components were all modeled in the software environment, allowing them to perform vibro-acoustic computations with strong coupling. This enabled a better understanding of acoustic phenomena in order to continue providing leading-edge acoustics solutions for exhaust systems.
Equipment with fans, turbochargers and HVAC systems creates a high noise level. This is an issue for heavy machinery companies because a larger engine requires a larger cooling fan, which makes more noise. Noise in both the inside field and the outside field can be calculated virtually. An example of this is John Deere engine cooling fan case. In construction, forestry, and agricultural applications, engine cooling fans create noise that often dominates the total machine noise. The noise must be well managed to pass international regulations for machinery products. Using acoustic simulation, it was possible to compute the aeroacoustic noise source and its propagation. In this way John Deere was able to reduce the development cost by integrating aeroacoustic predictions in the development cycle thanks to good correlation between simulation and experiment.
Noise can also be coming from vibrating cabin structure through mounting points. With acoustic simulation it is possible to study the structure borne noise propagating through mounting points and decide how to place more isolating windows and provide interior noise absorption. For example, Hyundai knew that its target audience was demanding silent cars, and road noise is one of the most important noise sources. Hyundai had to know how road noise was being transmitted from the road to the driver’s ear. To do this, Actran and Nastran were used together to model the car body. Airborne and structure-borne noise were studied. As a result, Hyundai was able to reduce road-noise transmission into cabin through vehicle trim design.
To conclude, acoustic simulation is allowing users to do less expensive and faster product development by reducing the number of physical prototypes required. It also allows companies to improve acoustic comfort, creating a competitive advantage and making it easier to comply with international and local standards. With this software users can get reliable acoustic simulations and have full confidence when trying out new designs.