Reverberation Time Calculator

What Is Reverberation Time (RT60)?

Reverberation time is the time it takes for sound to decay by 60 decibels in a closed space. It is a key parameter in room acoustics that influences speech clarity, musical quality, and overall acoustic comfort. Our RT60 calculator allows you to accurately model and simulate this effect in real-time.

How Is Reverberation Time Calculated?

The reverberation time is calculated using two well-known acoustic formulas, depending on the room’s average absorption:

Sabine Formula (Low Absorption)

\[ RT_{60} = \frac{0.161 \cdot V}{A} \] where:

• V is the room volume (in m³)
• A is the total equivalent absorption area (in m²)

This is Sabine’s formula named after Wallace C. Sabine (1868–1919). He introduced the reverberation time concept in a pioneering paper published first time 1898 in Proceedings of the American Institute of Architects.

Eyring Formula also called Eyring-Norris (Moderate to High Absorption)

For more absorbent rooms, the Eyring formula is more accurate:

\[ RT_{60} = \frac{0.161 \cdot V}{-S \cdot \ln(1 - \bar{\alpha})} \] where:

• V is the room volume (in m³)
• S is the total surface area (in m²)
• \(\bar{\alpha}\) is the average absorption coefficient

Limitations of Sabine and Eyring Models

For the calculations of reverberation time in enclosed spaces, it is assumed that the sound field is diffuse.

The Schroeder frequency is known as the frequency limit between modal and diffuse field. It means that above this frequency the sound field is considered as diffuse and Sabine/Eyring calculations can be applied. \[ f_{s} ={2000}\times{\sqrt{\frac{T_{60}}{V}}} \] where:

• V is the room volume (in m³)
• T₆₀ is the reverberation time

The model is applicable for regular shaped volumes: no dimension should be more than 5 times any other dimension

Another condition is that the absorption should be evenly distributed on all surfaces, absorption coefficient should not vary by more than a factor of 3 between pairs of opposite surfaces, unless some sound scattering objects are present;

Sabine Calculations are more adapted for low averaged absorption coefficient the room (alpha less than 0.3). Eyring more for absorbent room (alpha >0.3)

It assumes also that not too many objects are present in the room, around a maximum of 20% of the volume of the room

To help the user, we introduce a Quality Factors for the model to take into account these limitations. These indicators have been created by us and it based on the criteria present in the ISO 12354-6 and references described below.

If these assumptions are not met, the reverberation time can often be longer than estimated or need to have an expert analysis.

Features of Our Reverberation Time Module

• 📏 Customizable room dimensions (length, width, height)
• 🧱 Define surface types: walls, floor, ceiling, with unlimited sub-surfaces
• 🎛️ Input absorption coefficients or select from predefined materials
• 📊 Visualize RT60 results in a clear interactive graph using and add your own RT values to copare
• 💾 Save, load, and manage multiple room configurations via your account

How to Use the RT60 Calculator

1. Enter your room dimensions in meters.
2. Add surfaces (e.g., ceiling, floor, each wall) and customize their absorption properties.
3. Use the graph to instantly view the reverberation time across octave bands.
4. Adjust surfaces or materials and see how it affects the acoustic response.

Who Is This Acoustic Tool For?

Our reverberation calculator is ideal for:

• Acousticians performing early-stage design analysis
• Architects designing performance or meeting spaces
• Home studio builders improving recording room acoustics
• Teachers and students in acoustics or audio engineering

It’s a powerful addition to our Room Mode Calculator and Diffuse vs Direct Sound Tool, making it part of a complete acoustic simulation suite.