fact21

How do they work?

Noise reduction materials can work in four basic ways.

1. SOUND ISOLATION -

stops sound from passing through by reflecting it.

Some heavy materials will stop a lot of sound, eg sheet metal, timber, masonry, plasterboard, glass, loaded vinyl. They may be used in double leaf constructions, in which case the air space needs to be as wide as possible

2. SOUND ABSORPTION -

soaks up sound so that it is not reflected.

Porous material, eg. open cell foams and fibrous materials such as fibreglass and rockwool, act as very good sound absorbers, by converting sound energy to a small amount of heat. However, as most allow sound to pass through them, they are poor sound isolators. Usually they are used in conjunction with a solid sound isolation material.
Sound absorbing materials often need a protective facing to prevent damage. Common facings include perforated sheet metal, perforated foil (sisilation) or perforated vinyl.

3. VIBRATION ISOLATION -

stops vibration energy passing from one point to another.

Materials that are naturally “springy” can be used to isolate a vibrating machine from a floor, wall or ceiling. For example: springs, rubber mounts, air cushions, pads or mats of rubber cork or fibreglass. Springy materials also act as a good buffer for absorbing impacts.

4. VIBRATION ABSORPTION -

soaking up the vibration by damping.

Some materials may be used to absorb vibration energy. A material which will not ring when tapped has a good internal sound qualities and can be used to absorb the ringing of lightly damped materials.

Sound damping materials include foams, rubber, soft wood and granular materials such as sand.

SOURCE: "Building Quiet", Worksafe, Western Australia, Workcover, Western Australia.

Note: Selection of the best isolator for a job is a specialised task.

Australian made hearing aids utilizing Swiss technology
proudly sponsoring the Farm Noise and Hearing project to promote the
prevention of hearing loss in our community