Wave Dynamics GuidesReverberation Time Explained
What reverberation time is, how it is measured, typical targets for classrooms, offices and common areas, and how to control it.
In Short
Reverberation time is how long it takes sound to die away in a room after the source stops, measured as the time for a 60 dB drop (often called RT or T60). Long reverberation makes rooms noisy and speech hard to understand; acoustic absorption on ceilings and walls shortens it.
- Measured in seconds; shorter is generally better for speech.
- Controlled mainly by the amount and position of sound-absorbing finishes.
- Targets come from guidance such as TGD E (common areas), school design guidance and BS 8233.
- Testing on completion confirms the room performs as designed.
Why Reverberation Matters
In a hard room, sound reflects off every surface and lingers. Speech syllables smear together, people raise their voices and the room gets louder. This affects learning in classrooms, concentration in offices, comfort in restaurants and the noise reaching apartment doors from shared corridors.
Typical Design Targets
Targets depend on room use and size. Teaching spaces need short reverberation times so every pupil can hear the teacher. Open-plan offices and meeting rooms need enough absorption for privacy and comfort. Common circulation areas in apartment buildings are covered by Requirement E2 of TGD E. Sports halls, atria and performance spaces each have their own criteria.
How Reverberation Time Is Measured
We measure reverberation time using an impulse or interrupted noise source and calibrated meters at several positions, in line with I.S. EN ISO 3382. Results are reported across the frequency range and compared with the design target. Testing is common for schools, offices seeking BREEAM or WELL credits, and buildings where a planning condition or specification requires it.
How to Control It
- Acoustic ceiling tiles or plaster systems are the most efficient way to add absorption.
- Wall panels at head height help in tall rooms and where ceilings are exposed.
- Soft finishes and furnishings help, but rarely enough on their own.
- For exposed concrete soffits, raft or baffle systems keep thermal mass while adding absorption.
Frequently Asked Questions
What is RT60?
RT60 or T60 is the time for sound to decay by 60 dB. In practice it is extrapolated from a 20 or 30 dB decay, reported as T20 or T30.
Do schools need reverberation testing?
School design guidance sets acoustic performance standards, and testing on completion is the reliable way to show they have been met.
This guide gives general information and is not a substitute for project-specific advice. Requirements change, so always check the current regulations, guidance and your planning conditions. Ask our team about your project.
Jon Maguire (BSc Hons MIOA) brings over 8 years of expertise in acoustic consultancy, specialising in environmental acoustics with a focus on 3D modelling, assessments, and detailed design for industrial, commercial, and energy projects. He has lead noise assessments for key clients while thriving in multidisciplinary environments. Jon’s diplomatic communication skills are ideal for stakeholder consultation.
Jack is a Field Engineer at Wave Dynamics, supporting the delivery of environmental monitoring and acoustic consultancy services through detailed on-site fieldwork. He has hands-on experience in noise monitoring, vibration monitoring, and dust monitoring across a variety of infrastructure, construction, and environmental projects. Jack is involved in the setup, operation, and maintenance of monitoring equipment, ensuring accurate data collection in line with relevant standards and project requirements. He works closely with consultants and project teams, providing reliable field support that underpins high-quality assessments and reporting.
Aidan is the Director for all U.K Operations and has worked in multiple industries including for clients in the UK and internationally operating in the residential, industry, healthcare, education, and construction sectors.
