Estimate Sabine RT60 and first axial frequencies from rectangular dimensions, named-band equivalent absorption, and an entered sound speed.
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Create one ideal rectangular-room Sabine and first-axial-frequency record from measured dimensions, sourced band-specific equivalent absorption and entered sound speed without designing or certifying the room.
Record a transparent baseline before buying treatment.
Measure interior dimensions, name the band/configuration, source total equivalent absorption and enter condition-appropriate sound speed.
Gets an ideal hypothesis without a universal target or product prescription.
Keep geometry, band, absorption provenance, environment and model limitations auditable.
Save every input and compare the ideal RT60/axial frequencies with calibrated measurements at defined positions.
Can explain divergence without retrofitting coefficients to force agreement.
Know when the rectangular/Sabine baseline is incomplete.
Document openings, coupled spaces, nonparallel/flexible boundaries, furnishings and occupancy, then select a more appropriate method or professional review.
Does not treat the result as a seat map, treatment design or acceptance measurement.
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
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Measure the interior length, width, and height in feet and enter the sound speed for the environmental conditions being modeled. Openings, coupled spaces, sloped/nonparallel surfaces, furnishings, and boundary construction can make the rectangular model incomplete.
Volume = length × width × height; surface area = 2(LW + LH + WH)Provide a sourced total equivalent absorption area in square feet for one named octave or one-third-octave band and one occupancy/configuration. The tool does not invent a material coefficient or transfer one band to another.
RT60 = 0.049 × volume ft³ ÷ equivalent absorption ft²The three outputs are the first ideal axial frequency along each dimension. They are not peak/null magnitudes, listening-position predictions, tangential/oblique modes, treatment prescriptions, or measurements.
f₁ = entered sound speed ÷ (2 × dimension)Updated: August 2026
With 120 sabins in the named 500 Hz band and 1,130 ft/s entered sound speed, the ideal record reports 1,440 ft³, 792 ft², 0.588 s RT60, and first axial frequencies near 37.67, 47.08, and 70.63 Hz.
Keep separate records for the same room before and after a documented furnishing, occupancy, or treatment configuration. Compare the model with band-by-band measurements at defined positions; do not present the arithmetic as the measured change.
Use the result only as a rectangular baseline when openings, alcoves, nonparallel surfaces, flexible boundaries, coupled volumes, or substantial furnishings are present. An acoustics professional or measurement workflow may need a different model.
Use a traceable total equivalent absorption for the named band and configuration, and retain material area, mounting, test/source, occupancy, and uncertainty records.
Define use and acceptance criteria, measure the actual room band by band at specified positions/configurations, and involve the responsible acoustics, construction, electrical, fire, accessibility, or equipment professional where required.
This bounded worksheet combines two ideal models: Sabine reverberation time from room volume and an entered total equivalent absorption area, and first axial frequencies from rectangular dimensions and an entered sound speed. It does not derive absorption from material labels, predict response at a seat, size treatment, or certify a finished room. Preserve the named frequency band, source of every input, occupancy/configuration, and real measurement evidence.