Test The Limits

Absorbing away the cost of noise

By Adrien Mann

March 11 2016

Noise is a duality. On one hand, it can be soothing, inspirational, even emotional, like Beethoven’s 5th Symphony, or the fine-tuned thunderstorm of a Jaguar F-Type R (see Jalopnik article). On the other hand, it can be a nuisance, a discomfort, even a threat to our health. For electric car companies, low noise levels are a must to guarantee high levels of quality and low impact on the environment. In heavy industries, highly-powered machinery can generate health-threatening noise levels, if left untreated. Worldwide, governmental institutions have passed (and continue passing) laws limiting the noise levels in the vicinity of machines to ensure the safety of workers and neighboring citizens. (Watch a video on the challenges of noise management with many simulation examples of designs with and without absorbption materials including HVAC and power generators.)

 

With higher standards, stronger regulations and demanding performance constraints, product engineers have to push the design of their products to extremes never met before. And to do so, they have to use all possible manufacturing ammunition available. One chosen method is the use of sound absorbing material for noise control, such as foam, rock wool, etc. However, while it can be an efficient solution, it is extremely hard to quantify beforehand how the use of such materials will impact the noise levels generated by a given design, or how it will affect the performance of the system. Without the right prediction tool, the only remaining solution is to build a prototype and physically test it. But prototyping is costly, and can only happen extremely late in the design process, when most design features are already frozen. This approach to engineering is unfortunately closer to damage control than state-of-the-art product design.

 

Fortunately, innovative numerical methods are emerging providing engineers with the ability to predict early on how sound absorbing material will affect the noise levels and flow. For example, Exa’s patented Acoustic Porous Medium solution empowers engineers with the ability to assess the efficiency of sound absorbing material on noise levels, simultaneously ensuring that the material shape and location do not affect the overall performance of the product (often related to thermal protection, cooling flow, or flow performance - such as back pressure drop in an exhaust). With such predictive solutions, product engineers are now able to accelerate the design cycle, minimize the risks for failure and reduce the costs of late trial-and-error testing on costly prototypes.