The ANSI standard for classroom acoustics (ANSI/ASA S12.60) specifies recommendations for unoccupied classrooms. The recommended noise level and reverberation time are

The ANSI standard for classroom acoustics (ANSI/ASA S12.60) specifies recommendations for unoccupied classrooms. The recommended noise level and reverberation time are

• A. 10 dBA or less and 0.1 seconds or less
• B. 50 dBA or less and 1.0 seconds or less
• C. 35 dBA or less and 0.6 seconds or less
• D. 45 dBA or less and 4.1 seconds or less

Answer: (C)

ANSI/ASA S12.60 sets practical targets for classroom acoustics by looking at the room when it’s unoccupied. The goal is to minimize background noise and control reverberation so speech is clear when students and teachers are present. The two key measures are background noise level, expressed in A-weighted decibels, and reverberation time, which is how long sound energy takes to decay by 60 dB. Keeping the unoccupied background noise at 35 dBA or less means the ambient noise from sources like HVAC and equipment is low enough not to mask spoken words. A reverberation time of 0.6 seconds or less ensures that sound energy isn’t lingering too long; this helps consonants and syllables stay intelligible and reduces overlap between successive utterances. Together, these values create an acoustic baseline where speech can be understood more easily once people are in the room. The other options propose conditions that are either too noisy or too reverberant (or unrealistically silent), which would degrade speech intelligibility in a typical classroom. That’s why 35 dBA or less for noise and 0.6 seconds or less for RT60 is the best fit.

ANSI/ASA S12.60 sets practical targets for classroom acoustics by looking at the room when it’s unoccupied. The goal is to minimize background noise and control reverberation so speech is clear when students and teachers are present. The two key measures are background noise level, expressed in A-weighted decibels, and reverberation time, which is how long sound energy takes to decay by 60 dB.

Keeping the unoccupied background noise at 35 dBA or less means the ambient noise from sources like HVAC and equipment is low enough not to mask spoken words. A reverberation time of 0.6 seconds or less ensures that sound energy isn’t lingering too long; this helps consonants and syllables stay intelligible and reduces overlap between successive utterances. Together, these values create an acoustic baseline where speech can be understood more easily once people are in the room.

The other options propose conditions that are either too noisy or too reverberant (or unrealistically silent), which would degrade speech intelligibility in a typical classroom. That’s why 35 dBA or less for noise and 0.6 seconds or less for RT60 is the best fit.