SettingsSettings for this calculationUS
The vertical distance from the sound source (e.g. loudspeaker) up to the reflector panel plane.
Measure straight up from the sound source to the plane of the flat reflector panel.
The vertical distance from the listener's ear height up to the reflector panel plane.
Measure straight up from the receiver/listener position to the plane of the flat reflector panel.
The horizontal distance between the sound source and the receiver/listener position.
Measure the plan (horizontal) distance between the source and the receiver, ignoring their height difference.
Reflection point distance from source
22 ft
This uses the geometric acoustics (specular reflection) approximation, which is only valid when the reflector panel is large relative to the sound's wavelength — at lower frequencies (long wavelengths), diffraction effects dominate and this simple geometric method becomes less accurate. A full acoustic design should be verified by an acoustics consultant, especially for critical spaces like concert halls or recording studios.
- Angle of incidence/reflection from panel normal
- 65.56 °
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Acoustic Reflector Panel Placement Calculator: 22 ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Image-source (mirror) method for specular sound reflection: for a source and receiver on the same side of a flat reflecting plane, the reflection point along the plane is located at a distance from the point below the source equal to (horizontal distance × source height) ÷ (source height + receiver height) — this locates the point where the law of reflection (angle of incidence = angle of reflection) is satisfied, the standard geometric acoustics method used in architectural acoustic reflector design.
Inputs used
- Source Height Below Reflector Plane
- 10 ft
- Receiver (Listener) Height Below Reflector Plane
- 5 ft
- Horizontal Distance Between Source and Receiver
- 33 ft
Intermediate steps
- Angle of incidence/reflection from panel normal
- 65.56 °
Confidence note: This uses the geometric acoustics (specular reflection) approximation, which is only valid when the reflector panel is large relative to the sound's wavelength — at lower frequencies (long wavelengths), diffraction effects dominate and this simple geometric method becomes less accurate. A full acoustic design should be verified by an acoustics consultant, especially for critical spaces like concert halls or recording studios.
What this calculation does not cover
- Locates the reflection and never times it. What decides whether that reflection helps or hurts is the extra distance it travels compared with the direct sound: divide the path difference by the speed of sound, and past roughly 30 ms for speech — about 10 m (33 ft) of extra path — the ear stops fusing it with the direct arrival and starts hearing an echo. A geometrically perfect reflector hung too high is an echo generator.
- It places a panel and does not size one. The minimum panel dimension for genuine specular return grows with both wavelength AND the source and receiver distances, so the same panel that works close in becomes undersized as the room gets bigger. An undersized reflector does not simply return less — it returns only the top of the spectrum and lets the rest past, which is why it sounds thin and edgy rather than quiet.
- One source, one seat. The reflection point moves as the listener moves, so a flat panel solved for the middle of the seating serves the middle of the seating; the front and back rows take their reflection off a different part of the plane, or off no panel at all. Covering an audience means an array, or a curved or tilted surface, with the aiming solved separately for each element.
- The geometry assumes a flat plane parallel to the floor with both source and listener below it. Tilt the reflector — which is the usual move, because tilting is how the reflection gets aimed — and the two heights entered above stop describing the problem: the point and the incidence angle both shift, and a panel installed where this page puts it will send the sound somewhere else.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Image-source (mirror) method for specular sound reflection: for a source and receiver on the same side of a flat reflecting plane, the reflection point along the plane is located at a distance from the point below the source equal to (horizontal distance × source height) ÷ (source height + receiver height) — this locates the point where the law of reflection (angle of incidence = angle of reflection) is satisfied, the standard geometric acoustics method used in architectural acoustic reflector design.
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