Have you ever noticed how sound behaves differently in large spaces with hard surfaces (for example museums, atria) versus how it behaves in smaller spaces with soft surfaces (for example bedrooms)? How large spaces sound more ‘echoey” than smaller spaces?
Often shortened to “reverb”, this is the persistence of sound in an enclosed space after the original sound source has stopped producing sound. When sound waves are produced, they travel through the air until they encounter an object, which can reflect or absorb them. In a room or other enclosed space, the sound waves bounce off the walls, ceiling, and floor, creating a series of reflections that can continue for several seconds. These reflections can create a sense of space and depth in the sound, giving it a sense of “ambiance” or “room sound”. Reverberation is an important aspect of acoustic design and is used in many musical and audio production contexts, such as in music venues, recording studios, and even in virtual reality and gaming applications, to create a more immersive experience. Reverberation time in its truest form is the time that it takes for the sound to fall by 60 dB.
The level of reverberation in a space depends on a number of factors; including the size and shape of the room, the materials used in its construction, and the placement of objects within the space. Different types of reverberation, such as short or long reverberation, can be achieved by using different materials or by placing sound-absorbing materials in certain areas of the room.
This all depends on what the space is being designed for. This said it is often beneficial to include acoustically absorptive finishes in spaces used for speech (for example teaching spaces, offices, healthcare facilities) to help control reverberation and in turn aid speech intelligibility. Acoustic absorption generally takes the form of acoustics ceilings but can also be introduced as wall panels, baffles, or rafts.
In 2014, acoustics guru Trevor Cox set a new world record for the longest echo in a man-made structure in a subterranean oil tank in Inchindown, Scotland. After a single gunshot, the reverberation time was measured as over 112 seconds (more details here).