Playing Defense in the NVH League by Paul Goodes

As the manager of the noise and vibration consulting group at MTS, I see a lot of different customers with many different noise and vibration concerns. I would like to share with you an increasing trend I have seen in the automotive NVH (Noise Vibration and Harshness) field over the years: the shift from problem solving to problem containment.

It used to be that a problem would arise and someone with NVH experience (whether an internal resource or a consultant) would work on it until the problem was solved and design recommendations were made and implemented. With the increased requirements in today's automotive industry, Design and Release Engineers, Product Development Engineers and Manufacturing Engineers, all with little NVH experience, are responsible for addressing NVH concerns of their systems. How does this affect our NVH consulting business? Let me relate the NVH concerns of three customers I have recently visited. All are Tier 1 suppliers to the automotive OEM manufacturers of small sub-systems with noise concerns that can be basically approached in the same way.

The first one, a manufacturer of gear boxes, currently uses production line tests to catch loud samples so that they are not shipped to the customer. Interestingly, this does not result from an external (customer) requirement, but instead from internal quality control specifications. The problem the gear box manufacturer is facing is that its quality inspection system rejects parts that are not objectionable in vehicle and, worse yet, it passes parts that are noisy in vehicle. From our conversation, it was clear that the gearbox manufacturer does not wish to improve the design of its product, but instead is only interested in improving the design of the inspection system to make it more robust and cost effective.

The second case is that of a pump manufacturer whose customer (OEM) complained of whine in some of the pumps they supply. This pump is currently in production, there is no engineering specification from the customer and the pump manufacturer obviously needs to minimize the number of failed parts. The approach to the problem they are pursuing is double-sided: on one hand, they would like to show to their customer that the pump is not the issue, since the same pump is used in several other applications, none of which exhibits any whine. On the other hand, they do not want to lose the business and need to develop a cost effective validation test in case a whine concern arises.

My third visit was with a manufacturer of an actuator for a luxury vehicle. While their customer (luxury vehicle manufacturer) had not voiced any concern, internally their Chief Engineer had judged their actuator to have very poor sound quality. The Product Design Engineer I met with had benchmarked several other competitive actuators and found that their sound quality was very similar to that of their product. This led him to the conclusion that he does not need to improve the sound quality of the product, but needs to conduct a formal jury test to gather statistical evidence of this conclusion that can be used to convince his Chief Engineer.

All noise concerns, all basic mechanical devices and yet no one wants to solve the problem. So, what have I learned? NVH is no longer all about problem solving. Suppliers are in a tight and competitive market with little room for research. Their customers require products which are cheaper, lighter and quieter. While suppliers are doing their best at manufacturing cheaper and lighter parts, it is often too risky for them to redesign the product for noise after it has been optimized for function, cost and weight. Therefore, they need to put in place smart defense strategies. And this is where we, NVH consultants, are often asked to provide support in applying technology not to reduce the noise of the product, but to help the supplier in building their defense case against their customer.