What is Noise Vibration and Harshness Testing?

Noise Vibration and Harshness testing (NVH testing) is a critical component of any product during its design and development phase. Not only do manufacturers need to meet established requirements laid out by governing bodies such as The Environmental Protection Agency, but also severe noise and vibration are harmful to the human body and can be detrimental to the structural integrity of almost all consumer goods. In order to make products that last longer and sound better, physical testing should accompany all FEA models to ensure proper correlation, as well as give confidence in the design.

With the growing popularity of the electric car, automotive manufacturers will see an ever-increasing need to conduct NVH testing such asBuzz, Squeak & Rattle (BSR).鉴于缺乏发动机噪音，可能已经被忽视的许多声音现在可能会对客户变得滋扰，导致投诉和可能的回报。许多BSR问题可以在开发时期提前检测到具有简单的测试，例如通过开发的车辆轮廓或正弦扫描在一个消声室中的BSR振动器上运行组件。这些腔室设计成模拟“自由场”，其中允许声波在所有方向外自由传播但不返回。这种类型的测试可用于本地化不需要的声音的源或原因，允许制造商在产品成为保修期之前修改其设计。

BSR testing can be completed in one of two ways, subjectively or objectively. With a subjective evaluation, typically an individual or panel of individuals will listen to the noise generated by the structure under vibration and assess its perceived characteristics. Likewise, an objective test will utilize actual measurements along with hardware such as microphones to establish noise levels in several useful units including dBA, Sones, and so on.

Another critical aspect of NVH testing is Modal Analysis. Since all structures and mechanisms (including the human body) inherently have resonances to which they vibrate at, it is key to identify and avoid these frequencies whenever possible. When a system is excited at its resonance frequency, the amplitude at which it oscillates is at its maximum and can lead to premature wear of components, fatigue, or even sudden total loss of structural integrity. For example, aircraft manufacturers must comply with FAA Title 14 CFR Part 23, which requires the manufacturer to undergo ground vibration testing of all airframes to identify the structures resonances before an airworthiness certificate is issued. This process is completed on all new airframes, as well as changes to existing designs as any modifications to the structure will change the frequencies at which it resonates.

There are two principal methods in which modal analysis is conducted, either with force input via a modal tuned hammer or an electrodynamic shaker. Selecting the best option for structure excitation and boundary conditions to apply depends upon the structure tested and the specific data set of interest to product designers and developers. Regardless of the excitation method chosen, the primary information extracted is relatively the same, with resonances identified via the Frequency Response Function (FRF), between the force input and acceleration output on the structure.

元素提供的这些和其他类型的NVH测试包括：

• Sound Power and Sound Intensity
• Natural Frequency Analysis
• 刚性体特性的测定（CG，惯性惯性轴）
• Sound Quality
• 旋转机械的订单跟踪和分析
• 转移路径分析
• Static and Dynamic Structural Stiffness

元素experts use industry leading NVH testing methods, hardware, and software to assist our customer in developing safe, quality, compliant, and enjoyable products to bring to the marketplace.

Contact us today to talk to an expert or request a quote.