NVH is mostly engineering, but often objective measurements fail to predict or correlate well with the subjective impression on human observers.
In some cases, the NVH engineer is asked to change the sound quality, by adding or subtracting particular harmonics, rather than making the vehicle quieter.
Some problems are sensed visually, such as the vibration of the rear-view mirror or header rail on open-topped cars.
Typical instrumentation used to measure NVH include microphones, accelerometers, and force gauges or load cells.
Techniques used to help identify NVH include part substitution, modal analysis, rig squeak and rattle tests (complete vehicle or component/system tests), lead cladding, acoustic intensity, transfer path analysis, and partial coherence.
These early prototypes are very expensive, so there has been great interest in computer aided predictive techniques for NVH.
In contrast, when the phenomenon being considered occurs at relatively high frequency – for example, above 1 kHz – a statistical energy analysis (SEA) model may be a better approach.
Specific methods for improving NVH include the use of tuned mass dampers, subframes, balancing, modifying the stiffness or mass of structures, retuning exhausts and intakes, modifying the characteristics of elastomeric isolators, adding sound deadening or absorbing materials, and using active noise control.
Not-for-profit organizations such as the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) and Vibration Isolation and Seismic Control Manufacturers Association (VISCMA) provide specifications, standards, and requirements that cover a wide array of industries including electrical, mechanical, plumbing, and HVAC.