What is an Rw Acoustic rating?

When designing a noise wall or any other noise reducing structure, one of the most important factors to consider is what the Weighted Sound Reduction Index will be. A Rw acoustic rating is essentially a measure of how effective a noise wall is. Understanding this rating is substantially helpful when it comes to managing the expectations of what a noise wall will achieve, as well as in adhering to, and meeting legal noise mitigation requirements. In this article, we’ll explore what the Weighted Sound Reduction Index is, how it’s tested and how it affects a noise wall or sound proofing project. 

What is Rw?

Rw, or Weighted Sound Reduction Index, is an acoustic rating used to measure and indicate how effective a soundproofing wall, system or material is. Rw is based on the amount of sound that can be transmitted through a noise wall. 

Transmission is important because when it comes to mitigating sound from a highway for example, the lower the transmission, the more peaceful it will be for the neighbourhood next to it. The goal of noise mitigation is to decrease transmission, by using several different designs and materials that work together to form a soundproof system, like a noise wall, to protect that neighbourhood from the noise the highway creates. 

Noise walls are tested for sound transmission loss, which is calculated for each frequency (level) of noise. The higher the transmission loss, the better the sound insulation performance of that noise wall. The reduction of noise moving through the wall is known as Rw. 

Rw is measured in decibels (dB) and an increase of one Rw point is equivalent to a one less decibel that can be transmitted through a noise wall. 

How is a RW Acoustic rating achieved?

An RW acoustic rating is usually carried out by Acoustic Engineers, who analyse the frequency ranges of noise on either side of a noise wall or noise mitigating material. They achieve this by playing a series of sounds of varying frequencies on one side of the wall and using state-of-the-art equipment to measure the amount of sound that is transmitted through to the other side. 

Why is a RW Acoustic rating helpful? 

Knowing the RW Acoustic rating of a noise wall is the first step towards understanding exactly which acoustic walling solution is best suited to the source of the noise you are trying to mitigate. It will also help you meet any potential legal noise mitigation requirements that may apply. 

Legal noise requirements

To ensure that neighbourhoods don’t become victims of noise pollution, several rules and minimum legal requirements have been applied to sound mitigation, using the Rw measurement.  

The Australian Building Codes Board stipulates that a separating wall between most residential and commercial buildings should have an Rw of no less than 50. 

The VicRoads Interpretation and Application of Traffic Noise Reduction Policy (2005) outlines the objectives of limiting noise next to new or improved roads. For residential dwellings, aged persons homes, hospitals, motels, caravan parks and other buildings of a residential nature, the external noise level objective will be 63 dB. 

For more information on noise mitigation guidelines, this article features all the legal requirements around noise and noise mitigation as set out by Vic Roads. 

Acoustic rating professionals 

Effective noise management is a fundamental consideration when it comes to situations like neighbourhoods being situated next to highways or construction sites. Understanding the RW acoustic rating required for the noise mitigation project ensures that the noise wall that has been recommended will be both effective and meet the legal requirements. 

As leaders in the sound mitigation industry in Australia, our specialised Noise Walls have been crafted to address and minimise undesirable noise levels within commercial spaces. Our products boast an acoustic rating of Rw28, significantly exceeding the minimum legal requirement. 

These superior acoustic qualities make our noise walls the number one choice for the commercial industry. As an ISO certified operator, Wallmark has the ability to work on projects with both Government and private contractors, including VicRoads. Get in touch with a member of our team today. 

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