Two types of noise
There are two different types of noise that affect the acoustic environment in classrooms: Indoor noise and outdoor noise.
Indoor noise can be separated into two different sources: airborne sound and sound transmitted through the building itself.
- Airborne sound usually stems from human activities or mechanical noise in adjacent rooms. It travels through air, walls, floors and ceilings.
- Building-transmitted sound emerges from people or mechanical devices in spaces above or below, or through the ground.
- Indoor noise is usually combatted with interior sound reverberation reduction using furniture, carpets and other sound absorbing materials.
Outdoor noise stems from a building’s surroundings.
- The distance from noise sources has a major influence on the perception of outside noise; so, does the presence of barriers to noise such as buildings, trees, etc.
- Different sources create different types of noise. Traffic, for example, creates a low frequency noise, while birdsong is of a high frequency.
- Road traffic is the biggest source of outdoor noise. 13% of the population in Europe is disturbed by noise from road traffic.
Classrooms are never going to be – and nor should they be – entirely noise free.
Measuring sound pressure, open-plan offices are generally at approximately 70 decibels. If you’ve ever been in a room full of kids, you will know that children are not usually quieter than your average office worker, even when asked to sit down and focus.
The 70 decibels of an open-plan office are around 10 decibels higher than a simple conversation and 20 decibels above the standard sound pressure generated in a living room or kitchen. Rooms with many people in them tend to be noisy. And classrooms even more so.
So, a complete absence of noise is not realistic. Rather, the ambition should be to provide the right conditions for the production and reception of desirable sounds and sound levels.
In the case of classrooms, the teacher should be able to teach. And students should be able to hear the teacher - loud and clear.
In the coming sections, we will look at some of the steps designers and architects can take to ensure a satisfactory acoustic environment for classrooms. We will zero in from three different standpoints: external noise, internal noise and room shape.
External noise can be a source of frustration for teachers, especially as it’s difficult to control.
The Clever Classrooms study suggests that, whenever possible, classrooms should be situated away from busy areas like playgrounds, sports facilities and reception areas.
Traffic noise is often difficult to completely shut out, but can be reduced with the help of acoustic buffers such as trees and shrubs.
Windows with noise reduction qualities are key to reducing external noise. Rain noise reduction is especially important. Rain noise from windows alone has a sound pressure level of 40 decibels.
Internal acoustics can be improved by providing classrooms with large carpeted areas. If rugs seem unfit or impractical for the purpose, architects could consider tapestries or wall-hangings.
Other types of thick fabric/material can be used to decorate classrooms, even project work created by students using this type of material.
When reducing internal noise, wall-to-wall carpet or large rugs can be highly effective, but smaller-scale adjustments can also have a significant effect. For example, chairs and tables with rubber feet limit noise generated by movement. This is true for any room with tables and chairs, but especially so for a classroom full of restless children.
Classroom design should enable students to be seated closer to the teacher, meaning teachers are more easily heard. Rectangular rooms with a greater length to width ratio can usually accommodate such seating arrangements better, and they allow more options for presentations.
- Clever Classrooms (2015), Summary report of the HEAD project, University of Salford, Manchester
- Crandell, C., Smaldino, J. (2000) Classroom Acoustics for Children With Normal Hearing and With Hearing Impairment,Language, Speech, and Hearing Services in Schools, Vol. 31, 362–370, October 2000
- Picard, M., Bradley, J. (2001) Revisiting speech interference in classrooms, Audiology 2001, 40: 221- 244