RT60 Rating 101: Understanding Reverberation Time

What Is an RT60 Rating?

RT60 Defined: Time it takes sound to decay by 60 decibels in a space
Shorter = Better: Short RT60 improves clarity & reduces echo
Used In: Classrooms, auditoriums, gyms, studios, offices, & more

RT60, or Reverberation Time, is the most common metric used to assess how sound behaves within a space. It specifically measures how long it takes for sound energy to decay by 60 dB after the source has stopped. A long reverb time results in excessive echo and poor speech intelligibility, while a short RT60 creates clearer, more intelligible sound. Architects and acoustic consultants rely on this value to tune environments ranging from classrooms and offices to recording studios and gymnasiums.

Want to quickly estimate the reverberation time of your room design? Try our Room Acoustics Calculator to model reverberation time based on dimensions, materials, and surface finishes. It’s a great tool for architects, designers, and engineers working in early project phases.

How Is RT60 Measured?

Standard Equation: RT60 = 0.05 × Volume ÷ Total Absorption
Absorption in Sabins: NRC × surface area for each finish type
Measurement Methods: Predictive modeling or on-site testing

The most widely used method for calculating RT60 is the Sabine formula. This equation factors in the volume of a space and the absorption coefficients of its surfaces (measured in sabins). Reverberation time can be estimated early in the design process using modeling tools, or it can be measured in the field using omnidirectional sound sources and decay measurement equipment. Materials with higher NRC values reduce reverb time by absorbing more sound energy.

Recommended RT60 Rating by Room Type

Space Type	Target RT60 (Seconds)
Recording Studio	0.2 – 0.4
Classroom	0.5 – 0.7
Office / Conference Room	0.4 – 0.6
Auditorium	1.2 – 1.6
Gymnasium	1.5 – 2.5
Worship Space	1.3 – 1.8
Theater	1.0 – 1.4

The ideal RT60 value depends on how the space is used. Classrooms and offices require low reverberation times to ensure speech clarity. Larger spaces like auditoriums and churches can support slightly longer room reverb for a sense of warmth and resonance—but excessive echo can still be detrimental. Using this chart during design can help guide acoustic material selection.

Why RT60 Rating Matters in Architectural Design

Speech Clarity: Short RT60 ensures voices don’t overlap or become muddy
Comfort: Excess echo causes listener fatigue & distraction
Compliance: Some LEED, ANSI, & school design guidelines reference RT60

Reverberation time affects more than acoustics—it shapes how people experience a space. In schools, long sound decay time can interfere with comprehension. In offices, they reduce focus and increase stress. In performance spaces, they alter tonal quality. That’s why acoustic targets are often written into architectural specs or building codes. Understanding RT60 helps ensure your design supports its intended function.

Conclusion: RT60 Shapes the Sound of Every Room

RT60 is one of the most powerful tools in architectural acoustics—yet it’s often misunderstood or overlooked. Whether you’re optimizing for speech, music, or general comfort, keeping reverberation under control is essential. With the right absorption strategy, you can reduce echo, improve intelligibility, and design spaces that both sound and feel better. Don’t let reverb become a liability—design with clarity and purpose from the start.

FAQs: Reverberation Time in Architecture

What is a good RT60 value?

It depends on the room. For speech-focused spaces like classrooms or offices, aim for 0.4–0.7 seconds. For larger spaces like auditoriums, 1.2–1.6 seconds is ideal.