What is the connection between today’s teaching techniques and reverberation?
Reverberation, the reflection of sound waves off of hard surfaces, is a very common acoustic problem in older school buildings. In days gone by, when these buildings were constructed, students were expected to come in, sit down, and not speak unless spoken to. However today’s teaching techniques encourage group participation, discussion, and hands-on activities. Students are less likely to spend the day sitting silently, writing in workbooks, and more likely to be talking with their peers, moving from group to group, doing experiments, and working on computers. All of these activities can make the classroom a very noisy place, especially if the noise produced bounces around without being absorbed.
In order for the students to hear and understand what is being said, the teacher’s voice must stand out above any background noise produced by the activity. The louder the activity, the louder the teacher is required to speak. In the classroom, the activity noise and the teacher’s voice are reflected off of blackboards, tile floors, walls, and windows, and each echo interferes with the next spoken word. Although these reflections occur only milliseconds apart, the sounds continually crowd in on one another producing a layering effect that blurs the original sound. It is similar to the effect produced in a busy grocery store when a message is called out over the PA system. The message is loud enough to hear, but you may not understand what is being said.
How does reverberation affect students’ learning?
Reverberation makes listening difficult for all students but especially so for younger students who have shorter attention spans and are not as skilled at listening. Consonant sounds in particular (d or t? b or p?) become smeared and studies show that even for children with normal hearing, one word out of every four may be indistinct or even unintelligible. Students are forced to expend more energy simply trying to hear, or figure out what the teacher said, rather than thinking about the actual message. By the end of the day, both teacher and students have experienced considerable stress from the constant noise and continuous admonishments to "Keep the noise down."
Can reverberation be detected simply by looking at a classroom?
You can do a quick assessment by simple observation. Here is a checklist to help you determine if a classroom may need acoustical remediation. Reverberation may be a problem if:
- the room has a hard ceiling with no acoustical tiles
- the room has very high ceilings (greater than 10 ft.)
- the ceiling tiles have been painted, eliminating much of their sound absorbing capability
- the walls and floors are hard surfaces
How can reverberation be reduced in the school setting?
Reverberation can be reduced by adding sound absorbing materials to the walls, floor, or ceiling. Sound absorbing materials are porous; the sound waves enter the small cracks, holes, and fissures of the material, the sound waves are deflected and broken up, and the noise is reduced. To significantly reduce reverberation, up to 1/4 of the hard surface areas should be covered with sound absorbing material.
What products will reduce echo and reverberation in the classroom?
Materials that effectively reduce echo and reverberation must be porous, composed of small cells that allow sound waves to dissipate their energy within the material. While these materials can be very durable, they are often "soft" and thus are best installed, in a school setting, above the reach of students. Panels may be effectively installed above lockers in hallways and above the chalkboards and bulletin boards in the classroom. For larger areas such as cafeterias and auditoriums, the wall area alone may not be enough, so additional sound absorbing panels or baffles can be hung from the ceiling to reduce reverberation. Some of the acoustic panels described below can easily do light duty as bulletin boards, where tacks and pins can post materials that are changed infrequently. It is recommended that these panels not be painted as that will reduce their ability to absorb sound and compromise their effectiveness.
Consider the following features when selecting acoustic products for your specific application.
- Flammability (check the local fire codes)
- Resistance to molds, fungi, and bacteria
- Resistance to moisture
- Attractive appearance
- Durable, impact resistant