Page 148 - IGC BOOK

Damping – machine rotational speeds do not coincide with resonance frequencies of the
supporting structure, and if they do, hence damping is done to change the stiffness or mass of
the supporting structure to change its resonance frequencies.

Silencing – machines fitted with silencer on the exhaust to take noise away from the work area.

Path to Interrupt Transmission

Insulation - constructing acoustic enclosures walls around the noise source. Noise can penetrate
through acoustic walls to the normal environment. For example, industrial diesel generators are
constructed with acoustic walls to prevent noise escaping out.
Isolation – noise is transmitted to the supporting structure through vibration, separating
machine from the supporting structure using elastomeric materials such as rubber are often
mounted over steel springs to reduce vibration.

Absorption – using sound absorbent materials to absorb sound before it reaches the receiver
using thick lining material like cork, hard rubber, plastic, or viscoelastic materials such as silicone
rubber.

Receiver Protection
Acoustic Haven – it is not practically possible to reduce noise
in an apparently noisy area. To reduce noise to the receiver the
best practice is to enclose personnel in a sound reducing
enclosure.

Hearing Protection - Receiver control in an industrial situation
is generally restricted to providing headsets and/or earplugs
for the exposed workers. This is a last resort control and
requires close supervision to ensure long term protection of workers' hearing.

Administrative controls

Admin controls includes changes in the workplace or schedule that reduce or eliminate the
worker exposure to noise.

Examples:

• Operate noisy machines during shifts when fewer people are exposed.
• Limit the amount of time a person spends at a noise source through job rotation.
• Provide quiet areas where workers can gain relief from hazardous noise sources.

The employer must also carry out regular health surveillance to ensure that the employees are
not affected by exposure to noise, also to make sure that the existing controls are effective.
Noise health surveillance done through audiometry test.

ENSIGN | Unit IG2 – Element 5 – Physical and Psychological 8
Health