Engineering has many different branches, the branch of engineering that deals with sound and vibration is Acoustic Engineering or (Acoustical Engineering). Acoustic Engineering is very closely related to Acoustics and is the science of vibrations and sound. Acoustic Engineers are concerned typically with the following:

• How to make sounds useful.



• Using sound as an indication of some other physical property.



• The reduction of unwanted sounds.

Noise Control is the art of reducing unwanted sound. Engineers in the field of Noise Control work closely with engineers in most other industries to help ensure that their processes and products are quiet. In fact Acoustic Engineers (Noise Control Engineers) do a great deal of work in most noise sensitive or noise generating developments (developments involving the assessment and design of Road Systems, Buildings, Airports and Workplaces. There are many different documents and standards that the work must conform to, they state all the levels of performance that the Acoustic Engineer must achieve for each condition.

Noise Control

Noise Control is what Acoustic Engineering seeks out to achieve, it is an active or passive means of reducing sound emissions. Noise Control is often incentivised by environmental considerations, personal comfort or sometimes for legal compliance.

Some degree of detective work is required to accurately diagnose the cause of the sound or noise that needs reducing, the efficiency and practicality of the Noise Control is wholly reliant on this process.

Once the main source of noise has been verified the priority will always be to reduce the noise at its source, this is done by means of Acoustic Engineering.

Noise sources that usually need reducing can be put into two separate categories, Mechanical (Friction and Impacts) and aerodynamic (pneumatics, fans and combustion). The steps that are taken when an impact is causing a noise are as follows:

• Is there a possibility that the impact causing the noise can be avoided?



• If the impact can not be avoided is it possible to reduce the force of the impact?



• If this is not possible still or even as an extra measure can the impact be cushioned?



• The final step to use can be used if the above cannot or also as another extra measure for reduction, is it possible to prevent the vibration that is being generated by the noise from reaching the radiating surfaces

The above steps would be needed to ensure effective Noise Control from the Acoustic Engineering is achieved.

The four basic principles to Noise Control are as follows:

Sound Absorption – This will be a porous material, the material will act as a noise sponge. The noise Sponge converts sound energy into heat within the material. Fibreglass and Open-Cell Foams are common sound absorbing materials.

Sound Insulation – A mass barrier is introduced to prevent the transmission of noise. Metal, Brick and Concrete are common high density materials that can be used.

Vibration Damping – Sound Deadened Steel is a common material used and is applicable for large vibrating surfaces.

Vibration Isolation – Springs, Cork and springs are common vibrating isolators used for this process.