Noise, vibration, and harshness: What the machine is telling you.

Noise, vibration, and harshness: What the machine is telling you.

June 5, 2020 0 By Ray Bohacz

Within the engineering community, there is a discipline called NVH for noise, vibration, and harshness.

An experienced farmer can survey a field and determine the efficacy in terms of population, spacing, health, and other aspects of the stand. These being a useful metric of potential yield. In like fashion, an experienced engineer can listen to or feel an engine or machine and glean the absence or propensity for NVH.

This is a real-world example of two different levels of NVH. When you hear a cheap electric drill run in comparison to a high-quality unit with 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. At the same time, the low NVH example is smooth, quiet, and appears more powerful and responsive.

In the farm shop, it is vital to recognize NVH for two reasons:

While making purchase decisions.

As a diagnostic protocol.

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

For example, let us say you are looking at a fan system for a grain drying bin, an investment that you need to last for many years. 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? Does it seem to be out of balance and loud? These factors can be a valid predictor of the reliability of not only that component but others that the harmonic travel to, such as brackets and fasteners.

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

The effect NVH has on a machine and especially an engine is logarithmic; the frequency of the order of vibration that is causing the noise and harshness impacts wear exponentially.

Just as soil PH is not linear in its acidity or alkalinity and its impact on nutrient tie-up and plant uptake, so is NVH to machinery.

Listen to the machine

Your hands and ears are essential diagnostic tools when working on machines and engines. They can foretell a future problem, but it is a mindset you need to cultivate.

With the rare exception, a machine, component, or engine will announce its poor health through NVH, but most never acknowledge the cry for help.

I regularly touch and listen to engines and other machinery when they are operating to determine their condition.

For example, feel around the engine when running. Place your hand on the alternator, any pump, and the engine itself.

I like to do this from day one with a new purchase. This way, I have a mental and tactile history of what the machine or engine sounds like when all is well.

It is exceedingly difficult to identify a minute degradation if you have no tactile history. This same logic can be applied to a pump on a sprayer, a vacuum unit on a planter, the drive mechanism of a combine, or an electric motor on a center pivot. They all are willing to divulge their health if you listen and feel.

An excellent investment is a mechanic’s stethoscope. It will allow you audible access to components that cannot be heard otherwise.

A quick listen, especially if you have another of the same component for comparison, will reveal an abundance of information.

If you have electric drive meters on your planter, while in the shop, run them and listen for any anomalies. The same holds true for listening to circuits such as hydraulic and those going to a sprayer tip. They all talk, albeit in their own language.

It costs nothing to listen and feel your engines and machines. Pay attention to a change in valve train noise, bearing feel on accessories, and the general smoothness by touch.

When it comes to mechanical things, the most beautiful sound is that of smooth silence!