About this tool
The First Reflections calculator shows where sound from your source first bounces off walls, floor, and ceiling before reaching the listener. It uses the image-source method and computes the geometry in three dimensions: distance, delay (ms), and relative level (dB) for each point. The model accounts for source directivity (Q) and an aggregate wall reflection coefficient (α = 0.85 — typical room with painted gypsum).
Why it matters: first reflections arrive at the listener 1–30 ms after the direct sound and heavily affect stereo image and intelligibility. For monitors, reflections under 5 ms are critical — they smear localization and widen the image; for voice (podcast, video calls), reflections under 30 ms hurt intelligibility. The calculator ranks points by priority and tells you where to install acoustic panels.
How to read results: top-2 priority-1 points are mandatory locations for a 60×60 cm panel. If you have 6 or more priority points, add a ceiling cloud. The timeline shows the temporal distribution of all reflections; bars beyond 5 ms (for monitors) or 30 ms (for voice) can be ignored.
Common mistakes: treating by intuition instead of by computation; relying on "foam thickness" without realizing that reflections under 1 ms (stereo pair near a wall) cannot be cured by porous panels — you need geometry or diffusion; ignoring the floor (often the first reflection in nearfield) and the ceiling (especially in low-ceilinged rooms).
Next steps: for each priority point, open the Porous Absorber calculator — the "Pick thickness →" button passes the target frequency automatically. If the stereo image still drifts, verify monitor positions in the Speaker Placement calculator.
