RT60: the secret behind perfect acoustics

Do you know what RT60 is? Imagine you clap loudly in a room; the sound you hear after the clap, which gradually fades away, is the reverberation.

Understanding and controlling RT60 is fundamental to achieving optimal acoustics in any area, from a concert hall to an office or a recording studio. Here we explain its importance in creating the ideal sound environment.

Understanding Reverberation Time RT60

RT60 (Reverberation Time 60) is a key measurement and a crucial parameter in architectural acoustics. It is commonly used in acoustic studies to evaluate the sound response of a space and guide the design of acoustic treatment solutions.

Below, we will see how it is calculated, highlighting its importance in understanding and controlling the acoustic quality of a space.

Definition and Calculation

RT60 is the time it takes for the sound energy in a room to decrease by 60 dB (decibels) after the sound source ceases, according to ISO 3382. It is a significant indicator in the architectural acoustics of enclosed spaces.

The classic way to estimate it is using Sabine's formula:

RT60 = 0.161 × V/A. Where:

• V = volume of the room (m³).
• A = total absorption of the space (Sabins).

In practice, a partial decay of 20 or 30 dB (T20/T30) is usually measured and then extrapolated to 60 dB, since directly measuring a complete decrease may not be feasible in rooms with background noise.

For the actual measurement, a sound source (pink noise or impulse) and a Class 1 sound level meter are used, recording the drop in sound pressure level. Methods such as linear least squares regression are also used (Svantek, n.d.).

The Importance of RT60 in Acoustic Quality

Reverberation time directly influences how we perceive sound within a space. For example:

• An excessive value (greater than 2 seconds) causes an accumulation of reflections, blurs speech clarity, and generates an echo effect, significantly reducing intelligibility.
• A value that is too short (below 0.3 seconds) results in "dry" or lifeless acoustics, with a perception of flat and inert sound.

The right balance not only improves speech intelligibility in classrooms and auditoriums but also enhances musical perception and overall auditory comfort in any environment. Achieving such acoustic balance allows areas to be perceived as pleasant, functional, and emotionally satisfying (Svantek, n.d.).

RT60 Optimal for Different Spaces

Each type of room requires a specific reverberation time to achieve its ideal acoustic function. Below are indicative reverberation times based on the type of space:

• Classrooms and training rooms: 0.4 – 0.7 s
• Offices or meeting rooms: 0.5 – 1.1 s
• Recording studios: 0.3 – 0.5 s (in practice, lower values ​​are usually preferred to avoid unwanted reflections)
• Small theaters or auditoriums: 1.0 – 1.5 s
• Symphony halls or concert halls: 1.0 – 2.0 s
• Churches and cathedrals: between 2 and 10 s

Therefore, a classroom with a reverberation time of 1.5 s exceeds the indicated range, which can lead to poor intelligibility and listening fatigue. In contrast, a recording studio with a reverberation time of 0.4 seconds allows for clear and clean sound capture, without annoying echoes or reverberation.

This approach allows for adjusting the acoustic design of each space to be functional, comfortable, and adapted to its primary activity (Svantek, n.d.).

Manipulating RT60 for Optimal Acoustic Design

We will now explore how this reverberation time influences speech intelligibility, musical quality, and spatial perception in different types of rooms.

Materials and Strategies for Modifying RT60

This parameter can be effectively adjusted through a combination of practical strategies and appropriate materials. The goal is to achieve a balanced sound field by reducing reflected waves using absorbent and diffusive elements.

• Decorative acoustic panels with fillings such as mineral wool or foam, which absorb sound energy and reduce reverberation.
• Wooden acoustic panels. These are sound-absorbing panels. The wood is micro-perforated, allowing sound to filter through to absorbent inner layers, thus enhancing acoustic control.
• Modular or upholstered acoustic panels are easy to install and reconfigure, making them ideal for spaces requiring adaptability.
• Acoustic diffusers, such as grilles or curved structures, distribute reflections and prevent local echoes, complementing absorption for balanced acoustic conditioning.
• Furniture and textiles—rugs, curtains, and upholstered furniture—also help to discreetly control reverberation.

The key is to increase the effective sound absorption of the space to reduce continuous reflections and achieve a balanced and functional sound field. (Souza, 2020, 2021).

Measurement Tools and Simulation Software

Thanks to technological advancements, tools now exist that allow for the precise measurement and simulation of reverberation time in any space.

In this way, measurement tools for reverberation time (T20, T30, and T60) are used to obtain reliable data through methods such as modal decay and advanced algorithms.

To measure this parameter, a sound source that emits pink noise or an impulse signal (for example, a balloon or a gun) is used, along with a precision sound level meter to record the 60 dB drop in sound pressure level.

Advanced systems also allow for the calculation of the sound absorption coefficient of materials, using report templates, and the simulation of the impact of incorporating these materials into the room.

Regarding software, the solutions include, for example, a specialized module that generates standard reports on reverberation times, facilitating their analysis and comparison, even before installing sound-absorbing materials (Dewesoft, n.d.).

The RT60 and the User Experience in the Space

Beyond the technical data, the time it takes for a space to regain its silence directly affects the emotional, cognitive, and functional experience of those who occupy the area.

In classrooms and offices, well-managed reverberation improves concentration and reduces stress, as acoustic comfort optimizes communication, productivity, and the user experience. In homes, it improves rest and the feeling of privacy. In cultural spaces, such as theaters, it allows for an immersive, rich, and clear auditory experience (Habitaro, 2025; StudySmarter, 2024). Optimizing this parameter is synonymous with creating healthier, more efficient, and more humane spaces. Discover how to optimize it in your projects with acoustic panels and other solutions from Ideatec.

Bibliographic References

• Dewesoft. (n.d.) RT60 Measurement.
• Habitaro. (2025). What is acoustics in architecture and why is it key to comfort?
• Souza, E. (2020). How to improve acoustics in projects with exposed structures?
• Souza, E. (2021). Keys to improving acoustics in architecture: sound absorption and diffusion.
• Study Smarter. (2024). Acoustic Systems.
• Svantek. (n.d.) RT60 Reverberation Time.