Mechanical vibration isolation to reduce vibration transmission and structure-borne sound

Introduction to mechanical vibration isolation

Mechanical vibration isolation is common with mechanical equipment and machinery, like rotating equipment, i.e. pumps, electricity generators.

As mechanical engineers and acousticians, we are very experienced in reducing noise and vibration by design, and attempt to reduce vibration by optimising the design.

But sometimes it is necessary to isolate mechanical vibrations from transmitting into neighbouring structures.

What is mechanical vibration isolation?

Vibration isolation is a mechanism of isolating an object or structure from the source of vibration.

For example, a car engine is isolated with anti-vibration mounts from the chassis of a car to prevent the magnitude of the engine vibrations reaching the car chassis. If the isolation mounts weren't there, the car chassis would fatigue, and the cabin would be more noisy due to structure-borne sound and noise radiation.

What does Environmentally Sound Limited do to isolate structures and equipment from transmitting vibration

Our experience in vibration started with designing equipment and electronic instrumentation to survive in extreme vibration environments. There were several times that we wanted to use isolation mounts, or anti-vibration mounts, but the customer did not permit it in the design requirements.

Hence, us becoming more experience at designing for vibration and optimising structural dynamics.

However, when preventing structure-borne sound and vibration transmitting into buildings and structures, isolation is mandatory.

One degree of freedom model

It is easy to find the isolation curve of a one degree of freedom mass and spring model. But when it is a structure with several degrees of freedom, it is not just the mass, moments of inertia and vibration source that must be considered.

It's a complex system

It's the structural dynamics of the entire structure and how it behaves at different frequencies that is the true challenge. Which dictates how the structure behaves at different mounting locations.

For example, imagine a diesel electric generator that is mounted on a frame, which is isolated from the ground.

For some reason the vibration is getting through to the ground, but the isolation mounts were specified for that generator weight and vibration content.

The reason was that the frame was not rigid enough and was instead very flexible. At different frequency the vertical displacement at two of the mounts were very high, and the specified vibration isolation mounts were not effective.

It is the field of structural dynamics and modal testing that tis necessary at this stage, in order for us to stiffen the frame and isolate vibration from transmitting into the neighbouring structure and building.

Summary

Environmentally Sound Limited are vibration and noise consultants, as well as mechanical engineers. We have dealt with unwanted mechanical vibration in several industries for over 25 years.

If you need help with mechanical vibration isolation, please call us now.