“Statistically Speaking” – Classroom Sound Level and Learning

#Classroom Sound Level and Learning

Classroom sound levels and learning environments are critically important to children, families, and society.  Below we share information on this topic in effort to benefit all.

“The collective sound of human voices is the greatest noise problem in schools, according to noise level measurements.  The noise from multiple voices is significantly louder than machinery or other equipment.”  This quote is from hear-it.org.  Hear-it.org provides information to society regarding hearing and hearing loss to promote health and awareness and welcomes the use or quote of their articles (http://hear-it.org/school-noise-detrimental-hearing-and-learning).₍₁₎

CLASSROOM SOUND LEVEL TERMINOLOGY (THREE (3) OF THEM)….
Below are three (3) elements that contribute to the acoustics of a classroom.  Each must be addressed and evaluated to promote a quality learning environment.

Ambient Noise
One way to describe ambient noise is everything that is not the teacher’s voice (or primary speaker’s voice).

Reverberation
Another way to laxly say Reverberation is “Echo.”  Reverberation is sound bouncing off of smooth flat surfaces.

SNR – Signal to Noise Ratio
The SNR is how much louder the teacher’s voice is compared to background noises.₍₂₎  In general the teacher’s voice needs to be a minimum of 15dB greater than the background noise.

SOUND LEVELS AND LEARNING
Fortunately this has been a known and studied topic for many years.  The following is a brief summary of findings from a handful of studies.

New York City Daycare Centers and Elevated Trains
Preschoolers adjacent to elevated trains performed worse on psychomotor skills than children of centers in quieter neighborhoods.₍₃₎

New York City Elementary School and Trains
This setting allowed for a study within one (1) elementary school.  One side of the school was adjacent to train tracks the other side was not.  The students on the ‘train’ side had on average lower reading levels than the students on the ‘non-train’ side, averaging as much as a full grade level lower in some test groups.  After noise abatement methods were implemented on the ‘train’ side (rubber pads at train tracks, and acoustic ceiling tiles in the classrooms), a two year study concluded similar reading levels on both sides of the school.₍₄₎

New York Airports
Children who attend schools farther from major airports had higher reading scores than children attending schools closer to major airports.₍₅₎
 
CLASSROOM ACOUSTICAL CONSIDERATIONS….
A rule of thumb is ‘sound drops 6 dB every time the distance is doubled.’  For example if a teacher’s voice is 50 dB at the front row that is 4 feet away from the teacher, it will be 44 dB at the row that is 8 feet away, and 38 dB at the row that is 16 feet away.₍₂₎  This quickly illustrates how the sound of a teacher’s voice can become near the background level of a room, and not 15 dB above ambient noise that it needs to be for intelligible comprehension (if you are in the back row).

Ambient noise from exterior sources or internal to the classroom needs to be managed.  Above are results from studies that show the impact of ambient noise levels caused by exterior sources.  An analogy can be drawn to ambient noise sources within the classroom.  The students next to the exterior wall with ‘old’ ‘loud’ wall mounted induction units, unit ventilators, fan coil units, etc. will not have the same learning environment as students not hindered by this ambient noise.  The ambient noise from voices, HVAC systems, lights, and exterior sounds need to be managed to provide an adequate learning environment for all students.

STATISTICALLY SPEAKING….

REFERENCES:

1. Hear-it.org
2. The Institute for Enhanced Classroom Hearing
3. Hambrick-Dixon Developmental Psychology
4. Bronzaft & McCarthy, Environment and Behavior. Bronzaft, Journal of Environmental Psychology.
5. Green & Shore, Archives of Environmental Health