Good acoustic performance in educational environments is essential.

 

The ability of the educator to keep their student's attention can be significantly reduced if there is a high level of background noise or reverberation within the classroom.

 

 

Reverberation

Reverberation ('room echo') has a direct impact on speech intelligibility within a room. Factors affecting reverberation include room geometry and the distribution of absorbent materials within. Rooms with long reverberation times typically are large in scale and full of hard reflective surfaces culminating in a 'live' sounding acoustic environment. Contrastingly rooms with soft absorptive surfaces are commonly heard as acoustically 'dry' sounding. Overly 'live' sounding classrooms with long reverberation times can be frustrating for teachers and pupils alike as they must speak more loudly whilst still suffering reduced intelligibility. Young and hearing-impaired pupils in particular struggle with speech recognition in highly reverberant rooms.

Reverberation time or RT(60) is the most important variable when measuring the acoustic performance of any space. RT60 is the time required in seconds for the reflections of a direct sound to decay by 60dB. The lower this figure is, the less reverberant the room.

Acceptable reverberation times for classrooms:

  • Primary school classrooms - 0.6 seconds or lower

  • Secondary school classrooms - 0.8 seconds or lower

  • Classrooms for use by hearing-impaired students - 0.4 seconds or lower

All performance levels are detailed in the acoustic regulations for educational environments which is known as Building Bulletin 93 (BB93).

 

 

Background noise

Another key component in a teachers ability to deliver clear and intelligible speech is Background noise. Sources of classroom background noise include external noise from street traffic, corridors or neighbouring rooms and internal noise from the shuffling of chairs, desks and student noise. Commonly rooms with high reverberation times also suffer from significant background noise which is often brought about by the 'Lombard effect'. This phenomenon is described as the involuntary tendency for people to raise their voice in an effort to enhance audibility when overcome by reverberant noise.

With group tasks taking a higher prominence in today's classrooms, the taming of  background noise has become crucial in alleviating miscommunication.

Background noise is measured in decibels at a signal-to-noise ratio. This ratio compares the level of a desired 'signal' (in this case a speakers voice) to the level of background 'noise'. The higher the ratio the less of an encumbrance this noise is.

Acceptable signal-to-noise levels for typical classrooms:

  • Primary and secondary schools - +15db

  • Hearing-impaired students - +20-25db

All performance levels are detailed in the acoustic regulations for educational environments which is known as Building Bulletin 93 (BB93).

 

 

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