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SF Engine Man: Noise, Vibration, and Harshness

SF Engine Man: Noise, Vibration, and Harshness

Within the engineering community, there is a discipline called NVH. It stands for noise, vibration, and harshness. Like a farmer who can survey a field to determine a good stand, an experienced engineer can listen to or feel an engine or machine and glean either the absence or propensity for NVH. 

A real-world example of two different levels of NVH is when you hear a cheap electric drill run in comparison to a high-quality unit that has efficient bearings instead of bushings. They both turn the drill bit, but the difference in NVH is apparent. The poor-quality drill is rough sounding, noisy, and seems labored; the low NVH example is smooth, quiet, and appears more powerful. 

When comparing machines, tools, or engines for purchase, a low level of NVH usually comes with a price tag. It is costly, in relative terms, to quell the three devils of NVH. It is important to note that in most instances, NVH can determine life expectancy. 

For example, let’s say you are looking at a fan system on a dryer as an investment. Listen to and feel the motor, if possible. Does it shake excessively or feel coarse? Is it noisier than you think it should be? Does the fan turn smoothly and in a circular arc, or does it seem to be out of balance and loud? These factors can be a valid predictor of the reliability of that dryer.

When purchasing equipment, your hands and ears need to check for NVH, and then you can make an intelligent comparison between brands or models. 

The effect that NVH has on a machine, especially an engine, is logarithmic. In other words, the frequency of the order of vibration that is causing the noise and harshness exponentially impacts wear. Just as a soil’s pH is not linear in its acidity or alkalinity and its impact on nutrient tie-up and plant uptake, so is the detriment of NVH. 

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