Noise monitoring entails long-term sound monitoring without the need for human interaction. There are two main types of sound monitoring: workplace monitoring and environmental noise monitoring, each depending on the location of the sound source. Environmental noise monitoring is one of the most common kinds of environmental monitoring and is most often carried out using a monitoring system.
Decibels are measured on a non-linear or logarithmic scale. This means that instead of sound intensity increasing in equal increments, each sound interval increases by a factor of the base of the logarithm.
For noise, this means that a small change in the number of decibels can result in a significant change in the intensity of noise and hence its potential to damage a person’s hearing.
The 3dB ‘trading effect’ means for every 3 dB the sound level increases the impact on hearing health which is doubled. For example, 63 dB(A) is twice as noisy as 60 dB(A). The relevance of this is apparent when considering exposure to hazardous level of noise. For every 3dB the noise level increases, the exposure time must be halved to keep the worker safe from harm.
The 3 dB trading effect is accepted in most countries. Some countries like the USA use a 4 dB and 5dB trading rule.
The "action level" is a noise exposure level at which if met, the organisation is required to take action to reduce the level, however, the exposure limit value of 87 dB(A) which no worker can be exposed to.
The different levels mean different controls, the lower levels may require training and hearing protection whereas, the upper levels may require additional controls to reduce the level or the length of exposure time. These will be decided through carrying out a risk assessment, ensuring the noise limits have been assessed to determine the controls required.