What are acoustically unfriendly features?

The ceiling. This hard, flat ceiling provides an ideal (and unwelcomed) surface for sounds to reflect.

Reflections in the classroom are like echoes in a cave; words repeat over and over. Unlike a visitor to a cave, however, the teacher speaks continuously, and thus, the echoes interfere with the newly spoken words.

Ceiling to floor sound waves — or "flutter echoes" — could easily develop in this room. This unwelcomed element creates a ringing noise.

The effect is not unlike a band playing in a school gymnasium, where the acoustics are "live" or "boomy."

What are acoustically unfriendly features?

The hard-surfaced floor

Floors made of wood, concrete or tile have hard, slick surfaces. These surfaces reflect both unwanted noise (like the scraping of chair legs), and the desired sound (the teacher's voice).

But echoes are enemies of a teacher's voice — whether they are wanted or unwanted sounds.

Especially in classrooms like this (with hard walls, ceilings and floors), echoes repeat over and over. This "reverberation" cannot be overcome by the teacher merely speaking more loudly.

Rather — with all these sound waves bouncing around — this classroom is like an acoustic minefield for children struggling to listen and learn.

What are acoustically unfriendly features?

These windows are old with loose frames and thin panes. They are a poor noise barrier between the outdoors and classroom.

To make matters worse, a construction site just outside the room has brought a stream of booming trucks. At the very least, the windows should be closed to keep out some offending noise!

Also, the classroom has not been outfitted with drapes or shades to deaden reflected sounds. The many hard surfaces in the room create ample opportunities for echoes to develop.

What are acoustically unfriendly features?

The heating system. The steam radiator pops, hisses and clanks, adding to the background noise of this classroom.

Heating and air conditioning systems — particularly those in older schools — often feature too-small ducts or inefficient blowers that breed classroom white noise.

Although school budgets may not allow for replacement of older systems, it may be possible to improve the size of the ducts or install duct liners.

You may also have to consider turning off fans during lectures, and then turning them back on during study periods or small group activities to control temperature.

What are acoustically unfriendly features?

The teacher's position: Notice she is standing behind the desk, while the students are positioned across the room, near the back wall.

This arrangement creates an unnecessarily long distance between the source of sound (the teacher's mouth) and the destination (the students' ears).

Unfortunately, this teacher is trying to close the distance gap by raising her vocal volume.

Wouldn't it be less vocally fatiguing to merely move closer to the children?

What are acoustically unfriendly features?

1. The objects on the wall do nothing to soak up sound. Posters, student papers or chalkboards are not good sound-absorbing materials. When you speak, the sound is reflected.

2. The wall is made of concrete block. Materials such as brick, gypsum board (drywall) and wood paneling are highly reflective, so sounds are bounced around the classroom.

A good rule of thumb: the softer the object, the better its sound absorption will be.

3. To add to the problem, the students desks are hugging the rear wall. Unfortunately, the walls of this school were cheaply constructed, and the sound from the adjacent boiler room passes easily through them.

The situation could be (slightly) worse: This classroom space could be an "open pod" design, whereby no permanent walls were built at all!

What are acoustically unfriendly features?

The door in this room has been left ajar. Children's voices, slamming lockers, and tennis shoe squeaks from the hallway all pour into the classrom.

For this teacher, however, closing the door only resolves part of the noise problem. The door has a hollow core, and it does not fit well in the frame. It's a flimsy defense against the pandemonium in the hallway.