Noise and vibration testing

NVH (noise, vibration and harshness) is terminology that is often used in the automotive industry and is a key metric when developing new vehicles and has a direct impact on comfort, driving experience, brand perception, reliability and quality. Next to noise and vibration measurements and analysis it also includes subjective evaluations, measured either via jury evaluations or with analytical tools that can provide results reflecting human subjective impressions. Over time, the term NVH has also been adopted in other industries.

There are many reasons to perform noise and vibration tests apart from mandatory certification tests. In the past, it was often done when problems were found in the prototype or production phase, requiring fast results and high flexibility. In a modern engineering process, computer-aided engineering (CAE) is a driving methodology to assess performance on noise and vibration on virtual models before physical prototypes are available. A hybrid approach, where test data from real components or products can be used in virtual models for correlation or to build hybrid models to save computation time, became an effective way to combine the advantages of both real- and virtual worlds.

A typical measurement setup consists of both hardware and software components. Required hardware contains sensors to measure physical quantities (microphones, accelerometers, force cells) and a multi-channel data acquisition system to convert analog signals into high-quality digital values. The quality and usability of the data and, ultimately, of the results highly rely on the quality of the different hardware components. The measurement software is needed to configure sensor parameters, prepare the measurement setup, capture and store data, post-process and report the data into actionable results.

Several practical challenges and boundary conditions can play an important role in noise and vibration testing and the selection of the right equipment. For example, accessibility of sensor locations, cable length and layout (effect on data quality), the effect of adding sensors to the measurement object’s dynamic properties (mass loading), required ruggedness of the equipment for tests in laboratories or in the field, external conditions that are controllable or not, temperature influences, desired measurable frequency ranges for vibrations or acoustics and many more.