One of the most challenging aspects of building acoustics is that sound insulation and sound transmission paths are present in all three dimensions, when flanking transmission is included. If you have two rooms next to each other that requires a certain sound reduction index R´w in dB between them, the first thing that comes to mind is the directly separating construction, i.e. the wall between them or the floor structure. Most of the time, you will be correct, as this is often the most important transmission path. Hence, it is easy to miss that sound transmission occurs in many other places in a real building, which are not obvious at all when looking at a 2D drawing.

We are all wired in different ways and some people will find it natural to spatially visualize the structure and the relevant sound transmission paths, just by looking at a couple of 2D drawings. Personally, I am the complete opposite. When our civil engineering projects started to move more and more towards 3D modelling, I couldn’t be happier. Finally, I can visualize the junctions in a way that can reveal all transmission paths simultaneously. When working with CLT buildings, it is invaluable to simply click on a CLT element and highlight it in the model. That way, you can effectively scan for continuous CLT elements between spaces with high sound insulation requirements and ask the structural engineer to split them or you can ask the architect to draw an extra sound insulation layer. One should always be vary of continuous CLT elements, because they are highly sensitive to flanking transmission. If they are continuous in the vertical direction between stories, you can’t see that clearly on a 2D drawing from above

This type of problems is very well suited to 3D review by an acoustician and can help us discover more mistakes and optimize our buildings further. 3D models are also a great way to communicate on technical issues. We often take print screens of relevant details in the 3D model, and then we can draw arrows, text, mark areas such as walls that need extra insulation, placement of sound absorbers, floor structures etc. using a drawing tablet. Communication is a crucial component of civil engineering. If acousticians find it challenging to spatially visualize the 3D transfer of sound between rooms, just imagine how challenging it can be to communicate that same transfer with other disciplines!

/Rikard Öqvist, Acouwood