Vibrations, explained

Vibrations, explained by Geonoise Thailand

What are vibrations ?

When something is oscillating around a static position, we can say something is vibrating.

Most vibrations are undesirable, except of course those of a loudspeaker, which has to vibrate to produce sound.

Some examples of unwanted vibrations (though common) are vibration of houses near building sites, railways motorways, subways. Or precision equipment that is installed in a factory that is hindered by vibrations from a factory next door.

How can we measure vibrations ?

Vibration levels can be measured with accelerometers. An accelerometer will be attached to the material to be measured. With each movement of the accelerometer a small electric output (which will be amplified by an amplifier) will be send to a measuring instrument that transfers this electric output in a more easy to read result.

Most of the times it will be very useful to know the displacement and velocity of a vibration, rather than the acceleration. If we start with the acceleration level, we just have to integrate it to find the velocity. Another integration of the velocity will result in the displacement.

Solutions for vibration control.

Vibration problems are generally solved by simplifying the system as a number of springs and masses with damping.

If the vibration is produced by a motor, an easy way to solve this is adding weight to the motor (machine) or making it more stiff, so the forcing frequency of the motor will be well above the natural resonance of the machine on it''s support. The needed additional mass and stiffness can be calculated by acoustical engineers.

If the vibration source is with a fixed frequency, Dynamic Vibration Absorbers can be used. Here an additional tunes mass-spring combination is added so that it exerts a force equal and opposite to the unwanted vibration.

Active vibration control is just kicking off, with very promising results.

Geonoise Thailand, noise control Thailand and independent acoustical engineers Thailand