Sabine Formula Calculator

Sabine Formula Calculator Inputs

Enter six comma-separated values in this order: 125, 250, 500, 1000, 2000, 4000 Hz.

Unit System

Room Length

Room Width

Room Height

Occupants

Directivity Factor Q

Use 1 for omnidirectional, 2 for wall-adjacent sources, 4 for corner-related estimates.

Target Frequency Band

Target RT60 (seconds)

Person Absorption per Band

Sabins per person at each frequency band.

Extra Fixed Absorption per Band

Use this for curtains, seating, panels, or movable absorbers.

Floor Absorption Coefficients

Ceiling Absorption Coefficients

Front Wall Absorption Coefficients

Back Wall Absorption Coefficients

Left Wall Absorption Coefficients

Right Wall Absorption Coefficients

Reset

Formula Used

Sabine Reverberation Formula

RT60 = 0.161 × V / A for metric units

RT60 = 0.049 × V / A for imperial units

Where:

RT60 = time required for sound to decay by 60 dB
V = room volume
A = total equivalent absorption area in sabins

Total absorption area

A = Σ(Surface Area × Absorption Coefficient) + Occupant Absorption + Extra Absorption

Average surface absorption

ᾱ = Surface Absorption / Total Surface Area

Room constant

R = S × ᾱ / (1 - ᾱ)

Critical distance is estimated here with the entered directivity factor to help compare source behavior within the room.

How to Use This Calculator

Select metric or imperial units before entering room dimensions.
Enter room length, width, and height to define volume and boundary areas.
Choose the reporting band you want highlighted in the main result cards.
Provide six values for each absorption field in this order: 125, 250, 500, 1000, 2000, 4000 Hz.
Add occupant absorption and any extra fixed absorption from panels, curtains, or furniture.
Enter a target RT60 if you want the calculator to show design deviation.
Press the calculate button to display the result section above the form.
Use the CSV and PDF buttons to export your calculated summary and band table.

Example Data Table

Parameter	Example Value
Unit System	Metric
Room Dimensions	12 × 9 × 3.2 m
Occupants	18
Directivity Factor Q	2
Target Band	500 Hz
Target RT60	0.60 s
Person Absorption	0.30, 0.35, 0.45, 0.50, 0.55, 0.60
Extra Fixed Absorption	8, 10, 12, 14, 16, 18
Floor α	0.08, 0.10, 0.11, 0.12, 0.14, 0.15
Ceiling α	0.25, 0.45, 0.70, 0.80, 0.85, 0.90
Walls α	Front 0.04–0.09, Back 0.04–0.09, Sides 0.05–0.14
Example RT60 at 500 Hz	0.475 s
Example Total Absorption at 500 Hz	117.180 sabins
Example Critical Distance at 500 Hz	2.175 m

FAQs

1) What does the Sabine formula estimate?

It estimates RT60, the time a sound field needs to decay by 60 dB after the source stops. It helps evaluate room liveliness and speech clarity.

2) When is this calculator most useful?

It is useful during room design, renovation, acoustic treatment planning, classroom tuning, studio setup, auditorium checks, and early-stage engineering feasibility work.

3) Why are six frequency values required?

Absorption changes with frequency. Using six octave bands provides a more realistic view of reverberation behavior than a single average coefficient.

4) What is a sabin?

A sabin is a unit of equivalent sound absorption. One sabin equals the absorption provided by one unit area of a perfectly absorbing surface.

5) Should people be included in absorption?

Yes. Occupants can significantly increase absorption, especially in mid and high frequencies. Crowded rooms often show lower RT60 than empty rooms.

6) Why does the calculator show a room constant?

Room constant helps estimate steady-state sound fields and complements reverberation analysis. It is useful for broader acoustic engineering interpretations.

7) What does critical distance mean here?

Critical distance is the approximate location where direct sound and reverberant sound are equal. It helps assess microphone placement and speech intelligibility zones.

8) Can I use this for very absorptive rooms?

Use caution. Sabine works best in moderately absorptive spaces. Extremely dead rooms may be better evaluated with alternative models such as Eyring.