Assessing whether a room requires acoustic treatment

What causes reverberation in a room?

Hard, reflective surfaces like concrete, glass and wood can cause reverberation in a room. This happens when sound waves bounce around, creating multiple reflections that gradually decay as they are absorbed by other surfaces. It’s the combination of these reflections — rather than distinct echoes — that creates reverberation.

How does reverberation affect speech?

The sound reflections in a reverberant room make it harder to understand speech. Reverberation can cause syllables to overlap and words to become indistinct, leading to increased cognitive load and difficulty for listeners. This can be especially challenging for people who are hard of hearing or listening in a nonnative language. While people can adapt to moderate reverberation, excessive reflections will turn the room into a cacophony of overlapping sounds.

High levels of reverberation make it difficult for communication within a room. Improving the room acoustics will make it easier for meeting participants to communicate and improve the overall performance of any installed audio system.

How do I know if a room is too reverberant?

A simple way to test for reverberance is to loudly clap your hands. In a reverberant space this will result in a sharp echo of sound bouncing back quite readily. Your ears will pick up a distinctly echoed reflection. This is not quantifiable but can give you an indication of reverberance.

A more reliable way is to use the acoustic check tool in the Nureva^® App for iOS. It gives you a calibrated measurement of how long it takes for a sharp acoustic pulse — like the popping of a balloon — to decay to the point of inaudibility.

The resulting reverberation score (RT60 score) indicates the level of treatment the room may require. A long RT60 score indicates a room will require some additional attention to overcome the reverberation. A short RT60 score indicates reverberation is less of an issue.

An ideal RT60 score is between 0.2 and 0.6 seconds for a standard room with an area of up to 35' x 55' (10.7 x 16.8 m). In such cases, acoustic treatment should not be necessary.

What about ceiling height?

We noted earlier in this article that hard, flat surfaces are the main contributors to these sound reflections. Another factor to consider is the length of time it takes for a sound wave to reach the hard surface and reflect. Effectively, the higher the ceiling, the more time it takes for the sound to reflect, and the more it may contribute to reverberation.

Determining if a ceiling is too high is not an easy task. Other factors, like the surface materials in the room, the shape of the ceiling and even where a person is standing, should also be considered. Using the acoustic check tool in the Nureva App provides a quantifiable measurement that can provide some guidance.

When should the acoustic check tool be used?

Ideally, an acoustic check would be done with every installation, regardless of whether the room acoustics are in question. The Nureva App acoustic check tool can be used on an iPhone^® or iPad^® device to capture both the background noise level and the reverberation time. It combines background noise and reverberation measurements, providing an overall acoustic score that predicts audio performance in a specific location.

If a challenging room is identified, you can work with a local specialist to determine the level of acoustic treatments needed. Acoustic treatments will not only enhance speech intelligibility in a room, it will also improve the audio conferencing experience.