Rosenberg (2010) notes that there are multiple acoustic challenges in modern classrooms across the United States. Noise, reverb, distance, directionality, and teacher-student interactions (and various combinations of the same) all impact speech perception, comprehension, and academic accomplishment.
Children spend up to 75 percent of their school day performing “listening processes." Younger children have the least mature auditory systems (the auditory system continues to develop until approximately 12 years of age), less well-developed listening skills, and less knowledge regarding language. Therefore, the youngest children are the most vulnerable to poor classroom acoustics.
Noise sources that often impact classroom acoustics include heating, ventilation, and air conditioning systems (HVAC), external noise (traffic, playground, etc.), and sounds from adjacent classrooms. Reverberation is often a problem in the presence of hard ceilings without acoustical tiles, acoustical tiles that have been painted, ceilings higher than 10 feet, and hard surface flooring.
With regard to the signal-to-noise ratio (SNR), +15 dB is the minimum, but higher SNRs are desirable and beneficial, particularly for listeners with hearing loss, non-native English speakers, and for those with auditory learning problems.
Rosenberg notes that the "critical distance for effective listening" is the distance from the sound source (i.e., teacher) at which direct and reverberant sounds are of equivalent loudness levels. When the listener (i.e., child) is located at approximately one-third of the critical distance, reverb is generally inconsequential. If the listener is three times the critical distance, the direct signal is negligible and reverb is the prominent acoustic signal.
Rosenberg states that the role of the audiologist in the schools often includes advocating, serving as an information source, observing and measuring acoustic information, collaborating with facility planning teams, assuring acoustic access for those in need, and conducting efficacy measures
For More Information, References, and Recommendations
Rosenberg GG. (2010) Classroom Acoustics. Seminars in Hearing 31(3):188–202.