Simple Steps to Better In-Class Acoustics

Boys laughing in classroom

Educators are becoming increasingly concerned with sound in education, as it has become obvious that improved acoustics in classrooms leads to an improvement in student performance. Considering the reverse perspective explains why education environments are receiving more interest: if a sub-optimal environment damages learning, parents and educators are at risk of knowingly accepting second best for their children and missing vital opportunities for advancement.

At the root of this movement is that adults are finally beginning to realise how challenging the task of listening is for children. Children who are learning to read and write need to maintain high levels of concentration to comprehend what their teachers are saying. And they also need to be able to hear what is being taught to them in the first place. Yet up to one third of children in any primary school classroom on a given day may be put at a disadvantage by excessive noise and sound reverberation in the room. And another significant proportion will be struggling with gummy ears, colds and other temporary problems that take the edge off what they can hear.

A perfect acoustic environment is probably not realistic for schools on a budget or classrooms that actually need to be used in the real world. But that does not mean that parents and educators who are concerned about learning environments cannot take simple steps towards much better learning conditions.

Taking simple steps to better acoustics starts with separating the 2 main variables:

  • Noise Levels
  • Being Heard

Noise Levels

Before considering how to address unwanted noise in a class, the source of the noise must first be identified. Ideally and for best results, the source of the noise needs to be controlled at its source. This then directs the next steps – deciding:

  • What is the source of the noise
  • Is the source internal to the class or external
  • Can you control the noise source

Our picture below describes some of the noise that comes from outside the classrooms. Commonly sources of background noise include nearby land activities, noise from neighbouring classrooms and corridors, heating, ventilation, and air conditioning equipment (HVAC).

External noises are more difficult to control at source, so the best approach is to stop noise entering the room. Identifying these factors may require the services of an acoustic consultant. The PC Werth Education team offers an acoustics review service to help identify sound and acoustic problems in classrooms. This service is free, assuming the cost is rebated back as part of a wider package of activities from the company.

Noise sources

After taking the following simple steps to improve in-class acoustics, you will be better equipped to deal with all the common sources of noise found in schools and classrooms.

Approaches to Dealing with External Classroom Noise

1. Windows and doors – reducing noise from outside

Windows are a common source of noise because glass is thinner than brick and acoustically less absorbent.

Some tactics for reducing sound leaking through windows include the installation of storm windows, the replacement of  existing windows with thermal insulation units (This will improve energy performance, too.), and the installation of specially-fabricated sound-reducing glass. These are all capital intensive, but you may be able to make some difference with curtains for much lower cost, if the loss of light is not too extreme.

Doors produce a similar challenge to classroom acoustics – they are thinner than walls and introduce an acoustic void (a gap to most of us) around the door. The use of a good quality door, drop seals and gaskets, and the installation of special sound-control doors will lead to a clear reduction in noise.

Door drop seals

2. Heating, Ventilating and Air Conditioning (HVAC) system noise – reducing background noise

HVAC noise is a common cause of disturbing background noise in classrooms. Indeed, like many of us who are aware of a persistent disruptive noise – extractor fans in the kitchen, for example – teachers often resort to turning off the HVAC to reduce disruption, help concentration – and be heard. In the past, the use of fan-coil and similar through-the-wall heating and cooling units was popular in classrooms. This put the fan and compressor right in the room with the students. This became problematic because any noise source louder than a strong whisper masks consonant sounds in speech. It is precisely these types of sound that students need to correctly interpret the words they hear in order to learn effectively.

Being aware of HVAC noise is important, but it is particularly important that students with hearing loss are seated away from HVAC units, since their hearing instruments will often amplify the closest noise to them and not the teachers speech (which is why personal FM systems are so valuable).

Solving HVAC noise is not often a quick fix. Addressing reverberation will help (see this article), and any noisy through-wall, through-roof, or under-window units in the classroom should first be serviced and balanced to ensure that they are operating well. Going up in complexity, a custom built sound enclosure can be installed around the HVAC system in a classroom with added sound reducing lined ductwork to the unit to shift and reduce air distribution noise. If you are refurbishing a class, then it may be useful to replace the HVAC system as a whole with a newer, quieter model.

Approaches to Reduce Internal Classroom Noise

Where noise is generated inside the class, the same golden rule applies – address the source of the noise first. Teachers have been experimenting for hundreds of years in this area with varying degrees of success! Note that the correct response is definitely not to add more noise– i.e. teachers who raise their voices are adding to noise and creating a self-defeating (and health damaging) environment.

  1. Reduce Reverberation – reducing the impact of noise in class

Reverberation is the persistence of sound in a particular space after the original sound is produced, similar to an echo.

By layering “echoed” sound over newer sound, reverberation adds noise, mixes up the sound and makes listening more difficult for students, particularly for those who use hearing aids or have cochlear implants. Reverberation loves hard surfaces and the surfaces in a reverberant room typically do not absorb enough sound, thus allowing sound to bounce around in the room. This “blurs” sounds as they interfere with each other and arrive at the ear at slightly different times. Excessive reverberation makes understanding difficult, even if the volume of the signal is very loud. In fact, volume is likely to make the problem worse, as louder sounds reverberate for longer. Some reverberation can be removed from a room relatively easily; thus it is a good starting point for improving in-class acoustics.

Methods to reduce reverberation include:

  • removal or covering of hard surfaces – dressing the room better
  • the replacement of ceiling tiles with high-NRC-rated acoustical tiles,
  • the installation of a suspended acoustical ceiling if room height permits,
  • the installation of sound-absorbing panels on walls in the classroom.

If the classroom has a very high ceiling (~4 metres and up), acoustic treatments can be applied to both the ceiling and the walls. Carpet adds little to reverberation control, but may be useful for controlling noise created internally in the classroom, especially in pre-school and lower grades. The ultimate goal is to absorb sound that normally bounces over smooth and hard surfaces.

2. Other methods for addressing room noise

  • Position the classroom’s seating arrangement so that students are seated away from the noise source.
  • Use Hushh-upps or similar on the chair legs to reduce the noise of chair movements. Also encourage students to wear shoes with soft soles.
  • Avoid the use of temporary classrooms, especially those that use dry walls, since single layered dry walls do not absorb sound from outside well.
  • Turn off the whiteboard projector when you can, or move to LCD screens if possible. A sound enclosure around the projector would help if you can. Position students (and especially SEN/ Hearing Impaired) away from the projector and its fan.
  • Computers and printers produce quite a bit of sound – particularly when you have 2 or more together. Whenever possible, place all computer equipment in a separate room in the school. In order to lessen the sound from computer keyboards, use rubber pads or carpets under the keyboards.

Being Heard

There is no such thing as a silent classroom – thankfully! This means that no matter who you are or however acoustically perfect your class is, students further away from you are going to have a harder time hearing teachers than those close up. It is a simple law of physics that sound drops off rapidly with distance – as an inverse square: double the distance means ¼ of the sound.

3. Addressing classroom noise – making sure teachers can be heard.

This section is not just about the teachers’ voice, but includes making sure multimedia content, whiteboard, DVD or other desirable content can be heard.

Most classrooms can be improved in acoustic terms at very reasonably cost and effort. As part of the same exercise it is therefore important to consider the importance of being heard in class. Integrating all the various sounds in a class – and teachers’ voices in particular – is the job of a soundfield system.

Soundfield systems are voice-optimised, voice reinforcement systems for education – have a look at the Sound for Schools website for more information. Soundfield’s advanced AV technology disperses a teacher’s voice evenly around a class at a sensible volume that is at the right level to be heard above noise, without adding to the noise levels or suffering from reverberation. They also defeat noise in class by integrating all the sources of sound teachers want to hear, like the active whiteboard, so that students can hear and learn all of the time, no matter where the teacher is and no matter what direction the teacher is facing. Furthermore, all this can be done with less teaching effort, less interruptions, and less strain.

We hope that you’ve found the article helpful and that you have the necessary information to make your classroom a better learning environment!

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