Resource | 16.06.2023 | By Imran Mulla

4.1. Characteristics of sound sources and rooms

How sound behaves within the enclosed space and the listener’s ability to detect and comprehend speech is influenced by a number of characteristics of the sound sources and room design such as:

  • the shape and size of the room
  • construction materials
  • enclosed or open-plan classroom
  • height/slope of the ceiling
  • number and size of windows,and the thickness of the glazing
  • number and fit of the doors
  • floor covering, furniture, and soft furnishings.


Some sound will travel directly to the listener, some will be reflected, and some absorbed.

  • Direct sound – Direct sound travels directly from the speaker to the listener.
  • Reflections – Sound is reflected off hard surfaces and ‘bounces’ around a room causing reverberation (see section 4.2). The more reflective surfaces in a room, the longer the reverberation time (see section 4.3).
  • Absorption – Sound energy is reduced in a room when sound is absorbed by sound-absorbing materials.

  • Ambient noise – Ambient noise is the sound pressure level of a room. It is measured in decibels (dB) using a sound level meter. It is sometimes referred to as background noise.
  • Frequency – All sounds have frequencies. The frequency is the number of sound wave cycles per second and is measured in hertz (Hz). The more cycles per second, the higher the frequency. Typically, young adults can detect sounds between 20 and 20,000 Hz.

Speech sounds vary in frequency with most useful information for intelligibility between 1,000 and 4,000 Hz.


Considerations for QToDs

Listening is an individual experience. Each child will differ in how well they perceive they can access and comprehend speech in a classroom and how much they are affected by noise annoyance.

Questionnaires such as the Listening Inventories for Education (LIFE) UK or the LIFE-Revised (LIFE-R)R can be a useful guide as to how well a student (aged 7–14 years) perceives they can hear in different situations at school (see further information).


Further reading


Next pages in section 4

4.2 Room acoustics listening and speech intelligibility

4.3 Acoustic properties of a room

4.4 Acoustic standards legislation and guidance

4.5 Effects of poor acoustics

4.6 Improving room acoustics

Other sections