Echo and Reverberation
ECHO: We have at some point in our lives yelled “HELLO” into the canyon or cave, and heard a faint “hello” return. Sound travels at approximately 340 mts/ sec while the human brain endures the memory of a sound for just 0.1 seconds.
Hence to hear the perception of an echo the reflecting wall must be at least 17 mts away
REVERBERATION: This is obtained when the original sound wave returns to the listener in less than 0.1 seconds. This results in the listener’s memory of the original sound, merging with the reflection, and resulting in a prolonged sound wave.
When you sing in the shower (we know you have), your Pavarotti like sound is caused by reverberation, as the walls are less than 17 mts away.
When you are in the crowed pub you may struggle to be heard (or understood) as there are multiple sound source reflecting of multiple surfaces – all merging into chaotic elevated noise levels
Reverberation is quantified by Reverberation Time (RT60) which the time is taken for the original noise level to drop by 60dB.
| Reverberation | ||
|---|---|---|
| Too Little | Just Right | Too Much |
| (low RT60) | Sweet spot | (long RT60) |
| sounds within the same space appear dry and bland with restricted tonal balance | adds depth clarity ambience and crispness to original sounds | ambient noise levels start to escalate while the clarity of sounds deteriorate. For example “Cat” “Cab” and “Cap” may all sound similar in a reverberant room |
Studios and musicians can electronically add and adjust reverb time to achieve a particular or preferred “sound”, however such music now needs to be played and heard in a room with optimum RT60 to allow ideal listening.
Thermacoustic TC 417 & AF 90 are superlative sound absorbers that may be spray applied to reflective surfaces such as plasterboard dry walls, concrete slabs and metal roofs to achieve optimal Reverberation Times (RT60), while also assisting with the reduction of elevated sound levels.
The required amount of sound absorption surfaces such asThermacoustic TC 417 & AF 90 need to be calculated after considering parameters such as the dimensions of the room, the nature and levels of the anticipated internal sounds and the absorption achieved by other items such as carpeting, seating, people etc.
Australian Standard AS/NZS 2107 defines the Recommended Design Sound Levels and Reverberation Times for Building Interiors.
