Mitigating the effects of noise with sound maps
07 April 2016
Arne Berndt of SoundPLAN International LLC looks at how sound mapping software is used to mitigate the impacts of noise and what to look out for when selecting software.
Refinery sound map
There is a general acceptance of the dangers of excessive noise to human health and wellbeing, and even an agreed limit of when the noise becomes hazardous – 85 decibels (dB). As well as hearing loss, high levels of noise can result in sleep disturbance, cardiovascular disease and other physical disturbances in workers.
There is strong support in many countries for modelling the noise of buildings, infrastructure and transport both at the planning stage and for existing structures. Noise mapping software and the predictions they produce are now accepted as valid and an important part of the process of ensuring citizens are protected from excessive noise.
Only when you know where noise comes from and at what level can you take steps to mitigate it using barriers and other acoustic devices. Another important issue is alarm audibility within an industrial site, particularly in high hazard plants
The European Union has introduced the Environmental Noise Directive, which requires Member States to prepare and publish, every five years, noise maps and noise management action plans for:
• agglomerations with more than 100,000 inhabitants
• major roads (more than 3 million vehicles a year)
• major railways (more than 30.000 trains a year)
• major airports (more than 50.000 movements a year)
and focuses on three action areas:
• the determination of exposure to environmental noise
• ensuring that information on environmental noise and its effects is made available to the public
• preventing and reducing environmental noise where necessary and preserving environmental noise quality where it is good.
Scale of maps
This can mean producing complex and large scale noise maps, but noise mapping software is designed to cope with a huge range in scope and scale. Projects can range from industrial complexes which need to determine the 85 dB contour line in a plant – so workers know where to use hearing protection – through to country-wide noise maps to record the overall noise situation. At the levels in between, the software is widely used for a variety of types of projects, for instance architects determining the type of windows required for a hotel or road designers attempting to minimise the impact of a planned road.
What’s behind the map?
Small and medium size project sound maps can be created with all the data in a single file or they can be structured according to planning variant or topic. Larger projects should be structured geographically, which requires a tiling approach to allow the different layers to be examined.
Alarm system coverage inside a plant
Sound maps should depict noise levels in a straightforward way using coloured contour lines and facade dots according to a user set scale, so that the best option is clear. For example, if the goal of the investigation is to find the best route for a new road, comparing maps to the status quo is one possibility, and showing conflicts where the noise levels exceed the noise limit for a given area would be another way of showing results.
When using sound maps for country-wide noise, the map obviously depicts the noise levels for a very large area, so large that individual buildings can hardly be identified at the scale at which the map was drawn. Instead noise problems could be identified by tallying the number of residents exposed to specific noise levels, using a ‘Hot Spot’ presentation.
What to look for in sound mapping software
There are a number of suppliers around the world for sound mapping software, when choosing which one is best for you there are a number of factors to consider:
• Open source – Will you be able to transfer your data to a new software system should you need to? If it’s produced in proprietary software you’ll be locked into using that system or have to start again from scratch if you want to move.
• Good resolution – Is the map that’s created a high resolution image? Can you make out small details to help with noise mitigation planning or does it just give an overview of the situation?
• Information display – Does it contain the information or just present a picture? To be fully effective the information should be displayed within the map and different views should be available.
• Information manipulation – Are data files all merged or are they separate for easy manipulation and extraction?
• Meeting your requirements – Depending on the size of project, the software solution may change. For a small project a cut down version may be sufficient, but if the project grows will the software be able to cope and will a more complete version be compatible?
• Ease of use – Can you get it to do what you need it to do easily? Be careful though, if it seems very easy to use straightaway it may be because the software is basic and won’t be able to handle all of your requirements.
• Ongoing support – Will you get help to use the software after you’ve purchased it and how easy is it to upgrade it?
Functioning alarm systems for hazardous industrial sites
For a warning or alarm siren, the noise levels at any given point must exceed 66 dB and should be 10 dB louder than the ambient noise levels. Some horns have a strong directivity that must be considered when modelling alarm systems.
Many operators of hazardous sites also want to know the situation in the event that one of the alarm horns fails and how coverage is affected.
Keep these questions in mind when you’re researching noise monitoring software and you should get the solution you need whether it’s to better deal with noise for a single building or a whole country.