The Benefits of Directional Noise Monitoring
Noisy industry located near population centres can cause significant noise nuisance and is often required by their operating permits to routinely monitor their noise impact. While processes and equipment have evolved to reduce noise levels and minimise disturbance, some noise remains. In order to manage this impact, local regulatory agencies establish operating noise limits that the industry must not exceed, with exceedance often being subject to a fine. Many industrial sites therefore establish continuous noise monitoring systems to demonstrate compliance with limits in order to protect their operating licence. While these go a long way to help in some situations, their efficacy may be limited.
Industrial sites are often co-located with other industry and while one may be subject to noise limits, another may not. There are also any number of other unrelated sources of noise, including road and rail traffic and noise from the local community itself. Fig.1A shows a familiar problem. Industry A might be producing a noise level of 47 dB, well within the operating limits of 50 dB. However, noise measured at the boundary of the facility includes noise levels from other surrounding sources such as rail at 48 dB, road traffic at 50 dB, community noise at 45 dB and noise from Industry B 52 dB. In this case, a standard noise monitor would measure all of the noise and record a value of 56 dB – well above the compliance limit.
In Fig. 1B, a directional noise monitoring terminal set to register only noise from the direction of Industry A would record the noise level of Industry A at 47 dB, not causing a noise alert.
Other noise monitoring systems would register an alert, leaving the user to try and determine if they are responsible or not. With Directional Noise Monitoring, the user’s time is not wasted. Noise Sentinel effectively separates Industry A’s noise from other sources.
Another challenge exists with very large industrial sites such as mines. Noise restrictions are most often defined as noise limits at the boundary of the site with the community. For large sites, this may be far from the source of the noise, resulting in very low noise limits defined at the boundary, typically below 50 dB. The boundary is often closer to the community than the noise source and any noise activity such as road traffic, barking dogs or even bird song may trigger a threshold exceedance.
By separating noise coming from the direction of the user’s site while excluding noise from other directions, the user can reduce the number of false alerts from noise that have nothing to do them. This saves the user time, provides a more accurate assessment of their compliance with operating restrictions and helps them to put their noise impact in the context of everything else that is going on around.