Acoustic Glossary

We have created an overview of the acoustic terminology, that you might find when researching acoustic panels. All of it has been arrenged in an easy to look up glossary of the most commonly used words and expressions within sound and acoustics.


The properties of a room or building, which determine how sound is transmitted within it.

Decibel (db)

A logarithmic unit used to measure sound and electronics, indicating a ratio of power or intensity relative to a particular reference level. Its use is central to acoustics, particularly as people interpret loudness much closer to a logarithmic scale than a linear one. 0 db is about the lowest level most people can hear.


The rate at which a source produces complete cycles of sound waves. Frequency is measured in hertz: 1Hz = 1 cycle per second. Low-pitched sounds have low frequencies and high-pitched sounds have high frequencies.


People’s perception of the intensity of sound. Intriguingly, this does not reliably correspond to the level of the sound – our ears sense noise in different ways. This explains why certain repetitive noises are perceived to have lower ‘loudness’ than their volume would suggest.


When something oscillates in a stationary position it causes vibrations, which often create unwanted noise; for example, a washing machine on spin cycle. Vibration often poses a challenge when trying to reduce noise levels.


Refers to sound which bounces off a surface, or several surfaces. Overall, it is dependent on the texture and structure of the relevant surface(s). Reflection can significantly diminish quality of acoustic conditions – for example, concave surfaces are a particular challenge as they focus reflections on one area.


The prolongation of sound in a space caused by its reflection from multiple surfaces, from its emission until it becomes inaudible.

Reverberation time

The time it takes for reflections of a direct sound to decay by 60dB below the level of the direct sound. Key factors that affect it are: size and shape of the space and the materials used to construct it. Rooms used for speech typically require a shorter reverberation time as this enhances intelligibility. However, there is no ideal reverberation time, as different rooms have different functions.

Sound absorption coefficient

The sound absorption coefficient is a scalar representation of the amount of sound absorbed when striking a particular surface.

Speech intelligibility

The ability for speech to be understood. Indoors, reverberations play a key role in defining the level of intelligibility. Strong intelligibility is the ideal platform for a relaxing, productive atmosphere. For satisfactory communication, the average speech level should exceed that of any interfering noise by 6dB.