High vibration levels can cause machinery failure, as well as objectionable noise levels. A common source of objectionable noise in buildings is the vibration of machines that are mounted on floors or walls.
Obviously, the best place to mount a vibrating machine is on the ground floor. In this article, I am going to explain What is the theory of vibration Isolation and transmissibility in a detailed manner.
Vibration Isolation Theory:
- Unfortunately (but fortunately for noise control consultants), this is not always possible.
- A typical problem is a rotating machine (such as a pump, AC compressor, blower, engine etc) mounted on a roof, or on a floor above the ground floor.
- The problem is usually most apparent in the immediate vicinity of the vibration source.
- However, mechanical vibrations can transmit for long distances, and by very circuitous routes through the structure of a building, sometimes resurfacing hundreds of feet from the source.
- A related problem is the isolation of vibration-sensitive machines from the normally occurring disturbances in a building (car or bus traffic, slamming doors, foot traffic, elevators).
- Examples of sensitive machines include surgical microscopes, electronic equipment, lasers, MRI units, scanning electron microscopes and computer disk drives.
Transmissibility is the ratio of output to input.
Transmissibility (T) = output/input
- T>1 means amplification and maximum amplification occurs when forcing frequency (ff) and natural frequency (fn) of the system coincide.
- There is no unit designation for transmissibility, although it may sometimes be referred to as the Q-factor.
The transmissibility is used in the calculation of passive compensation efficiency.
- Vibration Isolation
- (PDF) Vibration Isolation: A Review
- Vibration isolation and force transmissibility – Nptel