Practical Approaches to Solving Noise and Vibration Problems

This article captures the strategies involved in addressing a system-level sound and vibration concern late in the design cycle. We start off with a discussion of the long-term goal of problem solving and the importance of leveraging the information gained during troubleshooting to improve the product development process for noise and vibration. A discussion then focuses on determining if the issue is due to nonconformance to a specification or a sound and vibration quality concern and how that information influences the problem-solving process. Baseline testing of the product is then reviewed, and test strategies are discussed to help identify the issue and quantify the sources and paths that contribute to the objectionable issue. A review of other problem-solving tools is included, and the article concludes with predicting the noise and vibration performance of a product and the role of test data in this process. A noise and vibration problem often shows itself very late in the design cycle or even after the product has been released. This occurs for a variety of reasons, including poor target setting, lack of design consideration and lack of reaction to warnings. Problems occurring this late in the design stage are often costly to fix and have limited design solutions. The outcome of any troubleshooting investigation should not only be to resolve the immediate concern but also to feed that knowledge back into the design process so the concern does not happen again. Noise and vibration issues can generally be separated into two categories: a problem caused by lack of compliance to a regulation or specification; or the product does not perform adequately in-situ, causing sound or vibration quality (SVQ) concerns. It is important to categorize the noise issue, because that determines the mode in which the product must operate when being evaluated. Measurements are made on the product during the appropriate operating conditions, and focus is put toward characterizing the problem. Analysis that results in overall vibration levels or even third-octave band data, which are common for specification-type testing, are of limited use in fully understanding the problem. Significant care must be taken at this stage to correctly characterize the problem, since this is the starting point that the investigation will be based on. Once the mode of operation is understood and the problem is characterized, testing to understand your product can begin. The goal of this part of the investigation is to determine the sources and paths within the product or system that contribute to the overall issue. An understanding of the sources and paths gives an understanding of the opportunities that exist to make design changes. A variety of problem-solving noise and vibration tools are at the engineer’s disposal: order tracking; modal analysis; noise mapping techniques such as sound intensity; near-field acoustic holographic and beamforming; and several others.