A classroom can look quiet without actually sounding quiet.
Hard floors, painted block walls, windows, whiteboards, desks and other reflective surfaces can cause a teacher’s voice to bounce around the room long after the original words are spoken. The result is excessive reverberation — commonly experienced as echo, muddiness or poor speech clarity.
For students, that can make it more difficult to distinguish one word from the next. For teachers, it can mean repeating instructions or raising their voices simply to be understood.
That is why reverberation time is such an important part of classroom acoustic design.
The ASA/ANSI S12.60 standard for school acoustics establishes acoustical performance criteria for classrooms and other learning spaces, including limits related to reverberation and background noise. The current permanent-school edition is ASA/ANSI S12.60-2026/Part 1, published in September 2026 as an update to the long-standing 2010 edition.
RT60, or reverberation time, is the amount of time required for a sound level in a room to decay by 60 decibels after the sound source stops.
In practical terms, RT60 tells us how long sound energy remains active inside the room.
A classroom with a long RT60 may sound:
A shorter, controlled reverberation time allows spoken words to decay more quickly so the next syllable or sentence is not masked by reflections from the previous one.
For learning environments where speech communication is critical, that distinction matters.
The established S12.60 classroom criteria commonly used in school acoustic design divide core learning spaces according to room volume.
For core learning spaces with an enclosed volume of 10,000 cubic feet or less, the established maximum reverberation-time target is:
RT60 ≤ 0.6 seconds
A room measuring 30′ long × 30′ wide × 10′ high, for example, has a volume of 9,000 cubic feet and falls within this category.
For core learning spaces larger than 10,000 cubic feet but no greater than 20,000 cubic feet, the established target is:
RT60 ≤ 0.7 seconds
The slightly longer allowable reverberation time recognizes the increased volume of the space while still maintaining conditions appropriate for speech intelligibility.
The 0.6- and 0.7-second classroom benchmarks have been widely used under previous editions of S12.60 and remain important reference points in classroom acoustic design. Projects being designed specifically for formal standards compliance should consult the current ASA/ANSI S12.60-2026/Part 1 requirements.
A difference between a one-second classroom and a 0.6-second classroom may not sound significant on paper.
Acoustically, it can be substantial.
Speech consists of rapid sequences of consonants and vowels. When reflected sound remains in the room too long, those reflections overlap with the speech that follows. Consonants — which contain much of the information we use to distinguish words — can become especially difficult to recognize.
A teacher may be speaking loudly enough, yet students can still struggle to understand what is being said.
Reducing reverberation addresses that problem by absorbing reflected sound energy instead of allowing it to continue bouncing between hard surfaces.
Reverberation is only one part of classroom acoustics.
Historically, S12.60 has also established a maximum one-hour-average A-weighted background noise level of 35 dBA for core learning spaces up to 20,000 cubic feet.
Sources can include:
This distinction is important because sound absorption and sound isolation solve different problems.
Acoustic panels absorb reflections inside the classroom. They do not, by themselves, prevent noise from passing through a wall, door, floor or ceiling assembly.
If the problem is echo and excessive reverberation, absorption is generally the appropriate treatment.
If the problem is noise transmission from another room, the building assembly may instead require improvements in sound isolation.
Classroom reverberation is generally evaluated in an unoccupied, furnished room, representing the acoustic characteristics of the completed learning environment without relying on students themselves to provide absorption.
The established S12.60 method focuses on the mid-frequency octave bands centered at:
500 Hz
1,000 Hz
2,000 Hz
These frequencies are especially important because they encompass much of the information needed for intelligible speech.
This is also why treating a classroom based simply on whether it “sounds echoey” is less precise than calculating or measuring its reverberation characteristics.
The room volume, existing surface materials and amount of absorption all influence the final RT60.
When excessive reverberation is the problem, one of the most straightforward solutions is to introduce additional sound-absorbing surface area.
NetWell Fabric Panels are cloth-wrapped acoustic panels designed specifically to absorb reflected sound energy inside a room. They can be mounted to walls or ceilings, allowing the treatment to be incorporated around whiteboards, windows, cabinetry and other classroom features.
NetWell’s 2-inch Fabric Panels carry an NRC of 1.15, with tested absorption coefficients of 1.24 at 500 Hz, 1.30 at 1,000 Hz and 1.21 at 2,000 Hz — directly within the frequency range important to classroom reverberation control.
That makes them particularly effective at absorbing the reflected speech energy responsible for excessive classroom reverberation.
Fabric Panels are also:
NetWell currently offers 44 standard fabric color options, allowing acoustic treatment to complement an existing classroom rather than making the room look like an acoustical laboratory.
This is where classroom acoustic treatment becomes more than simply hanging a few panels on the wall.
The correct amount of absorption depends on:
Room volume + existing absorption + surface materials + target RT60
A classroom with carpet, acoustic ceiling tile and upholstered furnishings may require substantially less supplemental treatment than an identically sized classroom with concrete floors, painted block walls and a hard gypsum ceiling.
Likewise, two classrooms with identical floor dimensions can require different treatments if their ceiling heights are different.
Adding too little absorption may improve the room without actually bringing the reverberation time down to the desired target.
That is why NetWell recommends determining the required coverage before the panels are ordered.
NetWell Noise Control can help schools, architects, contractors and facility managers determine how much acoustic treatment a classroom requires.
Through our complimentary Room Analysis, we evaluate the room dimensions, volume and existing surface materials and calculate an appropriate amount of sound-absorbing material for the space.
Rather than guessing at panel quantities, the goal is to establish a treatment designed around the acoustical needs of the room.
For schools working toward a specific RT60 target, let us know the desired reverberation time when submitting the project.
Students with hearing impairments or other communication challenges can be especially sensitive to reverberation and background noise.
Under the previous ANSI/ASA S12.60-2010 standard, core learning spaces of 10,000 cubic feet or less were required to be readily adaptable to a reverberation time of approximately 0.3 seconds for students with hearing impairments or other communication needs.
This is more stringent than the standard 0.6-second classroom target and reflects the greater importance of speech clarity for students who may have difficulty separating spoken words from background noise and reflected sound.
Certain specialized learning environments may require project-specific acoustic design beyond the standard classroom criteria.
Because ASA/ANSI S12.60-2026/Part 1 was recently published and supersedes the 2010 edition, projects seeking formal compliance should reference the current standard to confirm the latest requirements.
Classroom acoustics are sometimes treated as a comfort issue.
They are more fundamental than that.
A classroom is fundamentally a communication environment. If students cannot clearly understand their teacher — or each other — the room is not performing as intended.
Controlling excessive reverberation helps:
For smaller core learning spaces, the familiar 0.6-second RT60 benchmark provides a useful reference point. In larger classrooms up to 20,000 cubic feet, 0.7 seconds has historically served as the corresponding target.
If your classroom is excessively loud, reverberant or difficult to understand, NetWell can help determine how much absorption is needed to bring the room under control.
Submit your classroom dimensions through NetWell’s complimentary Room Analysis, or contact our help desk at 1-800-638-9355 to discuss your project.
NetWell’s Fabric Panels combine high sound absorption with an architectural fabric finish, making them an effective solution for classrooms where controlling reverberation and preserving the appearance of the room are equally important.
Available for wall or ceiling mounting, our Fabric Panels can be sized and configured around the specific layout of your classroom.
Learn more about NetWell Fabric Panels and start planning your classroom acoustic treatment today.
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