ANSI Standard S12.60 on Classroom Acoustics
Every day, thousands of students across the country are unable to understand 25 to 30 percent of what’s said in their classroom. Excessive noise and reverberation in a classroom interferes with a student’s ability to clearly hear their teacher.
Before reviewing the standard, it’s important to be familiar with the attributes of sound found in the classroom that affect a student’s ability to hear and learn.
- Direct Sound
The sound of a teacher’s voice traveling directly from the teacher to the student is direct sound. It is always beneficial in terms of speech intelligibility because it is not affected by anything in the room, making it clear and distinct.
- Reflected Sound
Reflected sound takes longer to reach the listener than direct sound because its path to the listener is longer. Reflected sound can be good or bad depending on the time delay.
- Reverberation Time
The overall effect of reflected sound is called reverberation, and the time required for reflected sound to become inaudible is called reverberation time. Short reverberation times are good for speech intelligibility.
Calculate Reverberation Time
- Background Noise
Any sound that is generated outside the building, such as playground activity, traffic and planes can be considered background noise. It generally intrudes in the classroom by way of the windows. Within the building, an HVAC system and corridor noise can contribute to background noise.
The New ANSI Standard
ANSI Standard S12.60 for Classroom Acoustics addresses the issues of both reverberation time and background noise and their effect on speech intelligibility by placing maximum permissible levels on each.
Under the standard, the maximum reverberation time in an unoccupied, furnished classroom with a volume under 10,000 cubic feet is 0.6 seconds, and 0.7 seconds for a classroom between 10,000 and 20,000 cubic feet. The maximum level of background noise allowed in the same classroom is 35 decibels (dBA).
The standard’s acoustical performance criteria and design requirements apply during the design and construction of all new classrooms or learning spaces of small-to-moderate size, and, as far as is practical, to the design and reconstruction of renovated spaces.
At the present time, the ANSI standard is voluntary unless referenced by a code, ordinance or regulation. However, school systems may require compliance with the standard as part of their construction documents for new schools.