Auditorium Acoustic Design Calculator

Calculate RT60 reverberation time, room modes, and clarity using the Sabine equation for auditorium design.

Inputs

Length (m)

Width (m)

Height (m)

Seating capacity

Avg absorption coefficient

Tab to move between fields

Results

RT60 (seconds)

1.06

Volume (m³)6,000

Volume per seat (m³)12

Total absorption (sabins)910

First axial mode (Hz)5.7

Clarity C80 (dB)0.1

First Mode Width8.6

First Mode Height17.2

How to Use This Calculator

Enter Length (m), Width (m), and Height (m).
Set Seating capacity and Avg absorption coefficient.
Review the RT60 (seconds) result.
Use Volume (m³) and Volume per seat (m³) to inform your decision.

How the result changes with Avg absorption coefficient

Avg absorption coefficient	RT60 (seconds)
0.14	1.73
0.37	0.92
0.64	0.59
0.86	0.45

What each input means

Length (m): Room length in meters.
Width (m): Room width in meters.
Height (m): Ceiling height in meters.
Seating capacity: Number of seats.
Avg absorption coefficient: Average absorption of walls/ceiling (0.1 = reflective, 0.7 = absorptive).

What each result means

RT60 (seconds): Reverberation time (speech: 0.8-1.2s, music: 1.5-2.5s).
Volume (m³): Room volume.
Volume per seat (m³): Ideal: 6-10 m³ per seat.
Total absorption (sabins): Combined surface and audience absorption.
First axial mode (Hz): Lowest resonant frequency along length.
Clarity C80 (dB): Speech clarity index (higher = clearer).

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Length (m) = 30, Width (m) = 20, Height (m) = 10, Seating capacity = 500 = 5 input(s) provided
Calculate RT60
RT60
1.06 = 1.06
Calculate Volume
Volume = lengthM * widthM * heightM
6000 = 6000
Calculate Volume per seat
Volume per seat
12 = 12

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