Blocking exterior sound to reduce noise pollution

What is exterior noise intrusion? Let’s get started with the basics

Managing noise from the exterior is a constant challenge for design professionals. In the built environment, noise, by definition, is any unpleasant or unwanted sound. Noise can come from myriad sources, just as when we looked at managing interior sound in our last article. External noise on the other hand, such as road traffic, aircraft, or even neighboring occupants are just a few examples of noise pollution (often referred to as environmental noise) and should be considered during the design phase of a project.

Increasingly, noise is recognized as a physical form of pollution, negatively affecting Indoor Environmental Quality (IEQ) by causing disruptions and having adverse effects on the health and wellbeing of occupants. In this article, the fourth in our acoustics series, we’ll take a closer look at blocking environmental noise specifically, how to reduce noise pollution and improve the indoor acoustic environment. We’ll also look at the sources of noise pollution and its impact on the quality of an indoor environment.

The way construction materials manage exterior noise is rated differently from interior sound – we’ll explain how and the reasons why. The article will also address the various guidelines in place to protect people against noise pollution. From there we present practical information all building and design construction professionals need to know to construct buildings with materials such as stone wool that help reduce external noise, and by extension, support positive IEQ. Let’s get started.

What is noise pollution?

Noise pollution, also known as environmental noise or sound pollution, is any sound that negatively impacts

 the health or quality of human or animal life. In the built environment, urbanization is largely responsible 

for the increase in noise pollution by bringing infrastructure and buildings – residential, commercial 

and industrial – closer together.

Buildings can be affected by multiple competing external noise sources. External noise pollution examples 

range from railways to streetcars, airports, busy roads, and highways. Yes, infrastructure is crucial to urban life,

 but the consequence is that it can be very noisy. The resulting vibration and traffic noise – not to mention 

human noise pollution – can all have a serious and negative impact, especially in densely populated areas.

The importance of noise pollution control should not be overlooked. Repeated exposure to noise may

 reduce sleeping hours, productivity and efficiency at work, the recovery of hospital patients 

and the learning environment for students in schools.

Regardless of the source, the goal is to keep outside noises out. There are unique characteristics 

and challenges for exterior sound, and as a result, different strategies for how best to manage it.

 Managing exterior noise starts with understanding how it’s measured before we jump into the sources 

and solutions for the prevention of noise pollution. More on that below.

How is environmental noise measured?

Just like all sound, exterior noise is typically measured in decibels. Because exterior sounds, especially 

in urban areas, often exceed 80 dB, they fall into the range of what is considered excessive or pollution. 

Creating a comfortable living space for building occupants means architects and designers need

 to take into consideration different methods to control sound. Outdoor-Indoor Transmission Class (OITC) 

is one such method of understanding how the insulated assemblies reduce noise around the building.

The OITC rating was originally created to measure exterior walls and their elements (windows and doors). 

OITC also provides a number rating for roofs, facades and facade elements that are subjected

 to transportation and other exterior sources of noise. The higher the number, the better the noise isolation. 

When choosing building envelope designs, using the OITC rating as part of your criteria for material selection 

will provide more accurate results in particular when lower frequency noises are expected.

The differences between OITC and STC (Sound Transmission Class) can be confusing if you’re not working 

with them every day, so we’ve created a table to serve as a reference for you. At ROCKWOOL, our assemblies 

are tested for both STC and OITC ratings to ensure assembly performance under different frequency ranges.

What is the difference between OITC and STC?

Outdoor-Indoor Transmission Class (OITC)Sound Transmission Class (STC)
  • Used for measuring external noise transmission into the interior,
  • Originally developed for roofing, exterior walls, and elements such as windows and doors, today it is the best sound rating system to use for these potential sound entry points, and
  • Measures sound transmission loss from 80 to 4,000 Hz.
  • Sound transmission rating for interior building partitions subject to various noises one could experience in high-rise buildings, including between units, between corridors or around mechanical service spaces,
  • Best sound rating system for measuring common sounds such as speech,
  • Measures sound transmission from mid to high-frequency noise sources, and
    Measures sound transmission loss from 125 to 4,000 Hz.

Let us know if you need support

Stone wool is a great acoustic insulator and is used in building assemblies to provide OITC ratings that help 

to minimize the impact of exterior noise on the indoor environment. ROCKWOOL has several OITC- and 

STC-rated wall assemblies that can meet the architectural specifications.

Our technical support team is ready to work with you in evaluating whether a particular assembly would 

satisfy the noise level reduction (NLR) you are trying to achieve. We’ll also provide you with a recommendation 

on the right acoustic solutions for your specified requirements. Consider ROCKWOOL a partner in your next project.

ROCKWOOL Technical Support Services

What are the primary sources of noise pollution?

Noise pollution comes in many from many sources and there are numerous examples in our everyday life. 

Noise sources that are in close proximity to a home or building have a major impact on what type of building

 envelope should be used. As a physical barrier between the conditioned indoor and unconditioned outdoor 

environment, the building envelope should be expected to maintain consistent levels of noise protection. 

Outdoor to indoor noise reduction is essential, especially when you’re looking for how to isolate or negate*

 the road noise and other sources of noise pollution in cities.

Five of the most common sources or examples of noise pollution are transportation, weather, construction, 

household activities, and heavy industry.

  • Transportation: In urban areas, traffic congestion is only increasing and proximity to transportation
  •  infrastructure such as large or busy highways, airports, railways, and other public transportation hubs 
  • leaves people susceptible to higher levels of noise pollution. Despite the noise of aircraft and commercial
  •  jets decreasing over the past few decades, there are areas where noise getting into buildings is continuing 
  • to create problems.
  • Weather: Have you ever been inside a building with a metal roofing system during a major storm or even 
  • a normal rainy day? When not properly designed for, the weather can be loud and distracting for those working indoors.
  • Construction: Construction sites are naturally very loud and are one of the most frequent
  •  sources of noise pollution. Those living in colder regions of North America will be familiar
  •  with the two seasons – winter and construction. Despite the fact that bylaws in many communities now 
  • prohibit construction during certain times of the day, heavy machinery, power tools, and people
  •  (whether talking or listening to the radio) make construction site-related noise an ongoing challenge.
  • Households: Common environmental noises from residential homes can include lawnmowers, 
  • leaf blowers, air conditioners, motorcycles, garage bands, and DIY construction or renovation projects.
  • Heavy Industry: Sound pollution from industrial operations doesn’t just have the potential to impact
  •  the hearing of workers on site, but without the proper sound abatement mechanisms installed, there can be negative effects on the surrounding neighborhoods.

So what’s the solution to noise pollution?

There is no one-size-fits-all approach to preventing noise pollution, but a good place

 to start is to consider the use of the space and the potential noise sources early on during the planning phase of the project.

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