Once machines are installed and a vibration problem is discovered, it is often very difficult and expensive to relocate the offending machine or sensitive area. Surface vibration WAVES are typically the culprit. The amplitude, or severity, of surface waves decreases by a function of at least (1/distance from vibration source)0.5. High frequency waves will dissipate over shorter distances than longer wavelength, low frequency waves. Vibration waves are further attenuated by damping losses CHARACTERISTIC of the materials they are travelling within. Steel, concrete, and frozen water/soil is efficient conductors of vibration. Surface waves can thus travel significant distance and still cause problems. It is most effective to reduce the amplitude of the waves at the source and at the sensitive area. The most cost efficient way to achieve isolation of the vibration waves is by using passive vibration isolators.

Many other methods have been employed to attempt to reduce the surface wave vibrations, with generally limited success:

1. Digging trench vibration barriers between the offending equipment and the sensitive area can reduce vibrations levels by 25% and sometimes more. Hard barriers such as concrete are generally ineffective, ALTHOUGH introducing any dissimilar material will result in some wave reflection. The barrier method is very expensive and great care must be taken to design the trench. If the trench is too shallow, the surface waves may pass below it. If the trench does not completely encircle the source, the vibrations may bend and reflect and bypass the barrier on the sides. There will be a shadow zone behind the trench where the vibration waves are reduced. Trenches may also be ineffective if the offending vibrations are compression waves reflecting from deep rock. Trench barriers will reflect some waves back towards the source resulting in increased vibration levels around the offending machine.
2. Replacing conductive soil or structures with more highly damped or more flexible connections at uneven intervals can reduce vibration transmission. This method is now common in pipe runs from vibration producing equipment within building structures. Within industrial plants these measures are generally impractical and the vibration reduction usually small.
3. Separating the foundation from the surrounding soil and making the support area of the foundation as deep as possible will reduce surface waves. Like trench barriers, this method is expensive and space inefficient. This method works on the principle that surface waves do not travel efficiently at depth.
4. Stiffening a vibrating structure that is in resonance can resolve problems in mezzanines and simple structures. A common problem is a multi-story or temporary office floors have low NATURAL frequency modes that can be excited efficiently by machinery shocks or, more commonly, PERIODIC vibrations. Machines like stamping presses and hammers introduce a high magnitude shock into the surroundings that cause a large transient wave to propagate. Many machines with rotating components such as high speed presses, vibrators, flywheels, generators, and motors can produce steady periodic vibrations. Stiffening the flooring of such structures to raise the natural frequency can alleviate the problem. Stiffening an existing structure is expensive because often the stiffness needs to be at least doubled to achieve noticeable results. When the problem is a machine with a very flexible arm such as on CMMs, EDMs, robotic welders or torches, and some mills, stiffening the arm can be a simple and effective solution.
5. Adding weight to the sensitive equipment is somewhat effective with diminishing returns as weight is added. Sometimes referred to as mass loading, this method increases the inertia of the equipment. This method is most effective when employed with passive vibration isolators to create a very low natural frequency system. In the form of a large inertia mass with isolators and a sub-foundation, the isolated system is termed an isolated foundation.

To avoid costly vibration mitigation measures it is best practice to be aware of vibration problems before a machine is installed. It is important to understand the frequency content of the source and the sensitive frequencies of the surroundings.

Once machines are installed and a vibration problem is discovered, it is often very difficult and expensive to relocate the offending machine or sensitive area. Surface vibration waves are typically the culprit. The amplitude, or severity, of surface waves decreases by a function of at least (1/distance from vibration source)0.5. High frequency waves will dissipate over shorter distances than longer wavelength, low frequency waves. Vibration waves are further attenuated by damping losses characteristic of the materials they are travelling within. Steel, concrete, and frozen water/soil is efficient conductors of vibration. Surface waves can thus travel significant distance and still cause problems. It is most effective to reduce the amplitude of the waves at the source and at the sensitive area. The most cost efficient way to achieve isolation of the vibration waves is by using passive vibration isolators.

Many other methods have been employed to attempt to reduce the surface wave vibrations, with generally limited success:

To avoid costly vibration mitigation measures it is best practice to be aware of vibration problems before a machine is installed. It is important to understand the frequency content of the source and the sensitive frequencies of the surroundings.