Room Acoustics & SBIR Planner

Room Acoustics & SBIR Planner helps you see why speaker and listener placement matters before you move a single speaker. Enter your room, place the speakers and the listening position, and read the geometry: where the room modes sit, the frequencies where a first reflection could cancel (geometry only), and where the first reflections land on the walls and ceiling.

It is a geometry-based planning and teaching tool for rectangular rooms. It does not measure your room, it does not predict how loud or flat it will sound, and it never gives a "score". Every number comes from the dimensions and positions you entered, and each result shows the assumptions behind it. Use it to plan what to try, then check the result in your real room with a microphone.

WHAT YOU CAN DO
• Draw the room to scale in the plan editor. Type exact positions or drag; undo and redo everything. Metres, centimetres, feet or inches.
• Room modes: axial, tangential and oblique frequencies, a mode list you can tap, and 2D pressure slices that show where a mode peaks and where it has a node.
• SBIR (speaker-boundary interference): the extra path and the first cancellation frequency for each speaker and each surface, with the distances that cause it.
• First-reflection points on the side walls, ceiling and front wall, with exact coordinates you can mark on the wall.
• Treatment panel placement: put panels on any surface, see their dimensions and distances from the edges. This shows where panels would sit. It does not claim how much sound they absorb.
• Never start blank: over 15 room templates (metric and imperial) with speakers and listener placed, three example rooms, furniture and door/window libraries, panel patterns placed from your reflection points, popular dimension-ratio presets (as reported in secondary sources, informational only) and measurement-note templates. All are starting points you can edit or delete.
• Notes, photos and screenshots of measurements taken elsewhere, kept separate from the app's calculations.
• Backup and restore: one .zip file with your rooms. You choose where it goes. Restoring never overwrites anything.
• English and Spanish, light and dark, large text, reduced motion, phone and tablet layouts.

FREE, FOREVER
One saved room with stereo speakers and a listening position, the 2D room editor, room modes with 2D pressure slices, front-wall SBIR, side-wall and ceiling reflection points for the central listener, basic panel placement, notes, backup and restore. Calculations are never degraded in Free.

PRO — ONE-TIME PURCHASE
No subscription. Pro adds unlimited rooms and layouts, the interactive 3D view of room modes, SBIR for every surface, multi-position listening-area coverage, detailed panel coverage and wall elevations, saved A/B layout comparisons, uncertainty and sensitivity ranges, advanced frequency controls, full project PDF reports (A4 or US Letter), panel schedules and mounting plans, attaching screenshots of external measurements, project duplication, and richer exports: a dimensioned SVG plan and a PNG setup card you can send to a client. The price is shown in Google Play in your currency. If Pro ever lapses, for example after a refund, you keep access to everything you already saved.

PRIVATE BY DESIGN
No account. No ads. No analytics. The app has no internet permission, so your rooms, notes and photos stay on your device. Files leave the device only when you choose to share them.

HONEST ABOUT WHAT IT IS
• Geometry is not measurement. A real room has furniture, openings and walls that flex; this model treats it as an ideal rigid box.
• Speakers are modelled as point sources at the acoustic reference position you enter.
• Reflections are ideal first-order mirror reflections. Treatment placement is a starting point to try, not a guarantee.

References: R. H. Bolt (1946) on normal-frequency statistics of rectangular rooms, J. H. Rindel (2021) on preferred dimension ratios, and Allen & Berkley (1979) on the image method.