First Reflections Calculator
The First Reflections Calculator traces sound rays from a source point and visualises how they reflect off surfaces in your model. This helps you identify early reflections that can cause comb filtering, flutter echo, or unwanted colouration — and figure out where to place acoustic treatment.
How to run
- Click the First Reflections button in the SketchAcoustics toolbar
- Click on any surface to place a sound source
- Configure the settings:
- Rays — number of ray paths to calculate (default: 20)
- Reflections — reflection order, 1–5 (default: 2)
- Dispersion — horizontal and vertical spread angles (default: 90°)
- Filter to Listener — show only rays that hit a marked listener
- Click OK to calculate
Reading the visualisation
Ray colours indicate reflection order. To see the colour coding correctly, enable Color by Tag in SketchUp’s Tags panel — SketchAcoustics uses tags to separate reflection orders into toggleable layers.
| Colour | Reflection order |
|---|---|
| Red | Direct sound (0th order) |
| Purple | 1st reflections |
| Blue | Higher-order reflections |
Listener placement
You can filter rays to only show those that reach a specific listener position. See Listener Placement for how to mark objects as listeners.
Tips
- Start with reflection order 2 — 1st and 2nd reflections are the most acoustically significant
- Narrow the dispersion angles to focus on rays aimed at a specific area (e.g. the listening position)
- Use Filter to Listener to cut through visual noise when your model has many ray paths
- Each time you run the tool, previous rays are replaced — you don’t need to clear them manually