Glossary of Acoustic Terms
| Term | Symbol | Description |
|---|---|---|
| Decibel | dB | Unit of measurement of sound. Human range is approximately 0 -130 dB |
| A weighted | e.g. dB(A) | Altered spectrum of frequencies to compensate for human hearing sensitivity. Humans are most sensitive to frequencies between 400 & 4000 Hz |
| Sound Absorption | |
Loss of sound energy (to heat usually) by a material or structure |
| Airborne sound | |
Sound that is transmitted through the air, this could be through walls. |
| Structure borne sound | |
Sound transmitted via the building structure such as floors. |
| Absorption Coefficient | NRC | A scale of 0 – 1 of how efficient a material is at absorbing sound energy where 0 is fully reflecting and 1 is fully absorbing, i.e. no reflection. See fig 1 |
| Absorption Class | A-E | A ranking of absorption where A is very good and E is poor. |
| Noise | |
Unwanted or unpleasant sound (not necessarily loud) |
| NRC | |
Noise Reduction Coefficient as a single figure |
| Reverberation Time | RT | Echo. Measure as the number of seconds taken for a sound to decay. See fig 2 |
Absorption Coefficients
(Armstrong Perla ceiling tiles)
Fig 1: Graph showing absorption data for a product at octaves
Reverberation
Fig 2: Recommended Reverberation Times for speech by room size.