Can you hear outdoor noise such as playground activity or traffic from a nearby roadway? Is noise from adjacent spaces adding to the background noise levels within the classroom?
The most common sources of background noise include:
- nearby land uses (traffic, construction, voices, and sirens)
- activities in adjacent rooms and corridors
- heating, ventilating, and air conditioning equipment (HVAC)
- classroom equipment (computers, printers, overhead projectors, aquarium pumps)
Isolated examples may be only occasionally disturbing, but constant noise will affect speech intelligibility in the classroom by competing with the desired speech signal. If you can hear street traffic, the teacher in the next room giving instructions, or the toilets flushing in the bathroom down the hall, the walls or the openings in them may not be adequately protected against noise transmission. Excessive background noise forces speakers in the classroom to raise their voices and this adds even more volume.
Background noise can be measured using a Sound Level Meter. As a frame of reference, the sound of breathing is 10 decibels and a soft whisper, 15 ft. away, is about 30 decibels. The current standard, as set by the Acoustical Society of America, for background noise in an unoccupied classroom should be no more than 35 decibels in all areas of the room.
Background noise can be reduced by making structural changes to doors, walls, windows, and floors
Windows – If disrupting noise (playground, school bus traffic, pedestrians) comes through the windows, Fixed Plexiglas Panels installed on the interior window frame can reduce outside noise heard within the classroom.
Doors – If hallway noise such as voices, footsteps, and bells is heard through the door, there are several products that will help reduce the sound.
Walls –If loud noise from a neighboring room is a problem (band practice, sports activities, power equipment in shop class) then wall modification with special sound blocking products is necessary. For the most economical use of materials, retrofit the room where the noise is produced. That way, noise does not carry out into the halls or adjacent rooms but is contained in the room of origin. Using a heavy Mass-Loaded Vinyl Barrier composite combined with 5/8 inch wallboard can dramatically reduce the amount of noise coming through the wall. Click here for more information on Mass-Loaded Vinyl Barrier composites and installation techniques for wall applications.
Is HVAC noise clearly audible? – Is it necessary for the teacher to turn off the HVAC for the students to hear the lesson? Equipment that hisses or rumbles louder than a loud whisper will mask the consonant sounds students need to correctly interpret the words they hear. If the heating/cooling unit is installed within the classroom, usually below the window, adding sound and vibration absorbing material inside the metal cover can reduce operational noise significantly. If the noise comes from a centrally located HVAC system, the solution is more difficult.
Floors / Ceilings – Impact noise occurs any time one object contacts another object with enough force to create noise. When impact noise carries through the floor structure of one room into the classroom below, it becomes a disruption for those occupants as well. One solution is to soundproof the floor/ceiling assembly in such a way as to prevent the sound from coming through. The second option is to minimize or eliminate the noise at its point of origin.
Activity Noise –Chairs scraping across the floor can be a significant cause of noise within a classroom. While it isn’t feasible to quiet the floors, it is possible to quiet the chairs! Hush-ups, used on the feet of each chair will dramatically reduce the noise of chairs scraping across the floor.