What to check when comparing airborne and impact noise ratings.

    19 February 2021

    Impact, airborne guide.

    Toolkit

    Let's get the confusing part out of the way first, on products you'll get some ratings like this;

    Impact L'nT,w (dB): 49dB
    Airborne DnT,w (dB): 49dB
    (Stats taken from the MuteMat®3) 

    L'nT,w – Weighted Standardised Field Impact Sound Pressure Level. This is a measure of the impact sound performance of a floor. It is an on-site or field test that measures how much impact sound reaches the receiving room below through the floor when a tapping machine is used on the floor above.

    DnT,w – The Weighted Standardised Field Level Difference. This is a single number measure of the airborne sound insulation performance of a building element.

    The confusing part, you want a LOWER L'nT,w rating, as you want less energy traveling through to the receiving room. Whereas your want a HIGHER DnT,w as you want more airborne insulation. Don't worry, I need to triple check this every time, and I've been working in acoustics for nearly 8 years from writing this.

    Whats the difference between airborne and impact?

    Noise is broken into two categories, airborne and impact noise. Just like a TV can be broken down into LCD, LED, OLED.

    Whats the difference, so let's first start with Airborne Noise. Airborne noise is the transmission of noise through the air and atmosphere. The prime examples of this are when people talk or having the TV. Airborne are those soundwaves traveling through the air to your ear. 

    In comparison to Impact Noise, which is the physical impact of an item or material. A few examples of this include, footsteps, doors banging, dropping something or even furniture moving around. All of which are a solid material hitting the building. 

    "Which one do I need?"

     If you can hear someone talking upstairs, airborne. If you can "feel" people walking around upstairs, impact.

    Products to solve the issue.

    As I explained in the toolkit at the start, we need to look out for the ratings.  Either L'nT,w or DnT,w. In a scenario where those ratings aren't available, we can look at another factor. Mass and composition (product structure), if the product is of high mass (weight) we know it'll be suitable for airborne. For example our ReSound Board weighs 28.44 kg/ m² so thats perfect for airborne. But when you look at the material it's a solid product, so. It'll only add to the impact noise. In comparison to the AcoustiLay 3, its a thin layer of vinyl and foam. Which soak up the impact energy.

    With regards to the ReSound Board, yeah it's a ceiling or wall product so impact isn't going to be an issue. But to dampen that noise, let's say from the floor above, using a IsoClip and channel will help. As the IsoClip gives a resilient layer to separate the board from the ceiling. 

    Conclusion

    As I said in our last post, it's always best to get in touch with a technical advisor if you're unsure. As it is possible to worsen your acoustics if the wrong product is being selected.

    Alex J
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