An acoustic strategy – Considering sound in indoor environments

by Tania Wannenburg
An acoustic strategy ECOPHON SAINT GOBAIN

By Lauren Kruger, concept developer for office environments at Ecophon Saint-Gobain.

Developing an acoustic strategy that encompasses both cultural and technical parameters, can help designers to thoroughly address the acoustics in a space and create a comfortable indoor environment.

Sound has a profound effect on people and can enable or disable activity within indoor environments. While this is increasingly acknowledged, sound and acoustics remain poorly understood.

Developing an acoustic strategy can assist in appropriately considering the acoustics within a design project.
Recreating a natural environment
Core to an acoustic strategy is employing ways to mimic the preferred, comfortable acoustic environment of the natural outdoors, indoors. An outdoor acoustic environment is characterised by an absorptive sky which does not reflect sound, organically shaped trees and bushes which diffuse sound, and soft groundcover which mutes sound that is generated by movement.

Indoors, this kind of environment can be achieved by ensuring that the ceilings and walls comprise adequate and appropriate acoustic absorption to limit the build-up of unwanted sound, diffusive elements to create variance in sound reflections, and lastly limiting the generation of unnecessary noise.

Once one understands the activity required in a space, it allows for adjustment that would ensure specific conditions are addressed or amplified. For example, a change in the geometry of a room or the materials specified for a ceiling may have a positive effect on the perceived clarity of speech within a training room.

Influencing behaviour
An acoustic strategy covers both cultural and technical aspects. Cultural aspects include simple instructions on how to promote good acoustic behaviour. This can, for example, help when explaining to a user that a certain space has been created for focus work and therefore telephone calls or impromptu meetings need to take place outside of that area.

Technical parameters
When looking at the aspects of an acoustic strategy, there are a number of parameters that are useful to understand. These can be used to define the acoustic performance of spaces:

•    Reverberation time, the most commonly used parameter, is the time (in seconds) it takes for sound to fall by 60dB.

•    Speech clarity is particularly important in a classroom or boardroom setting. The room should allow clear understanding of speech signals. One of the measures available for speech clarity is C50. This shows (in dB) the direct sound and the reflections that a listener’s brain registers in the first 50 milliseconds of the triggering impulse.

In open-plan offices, on the other hand, it is usually desirable to limit speech propagation since employees won’t want to be unnecessarily disturbed by voices.

•    The new acoustic standard, ISO 3382-3:2012, defines the methodology for measuring how far voices travel in an office landscape. Here, the spatial decay rate (D2,S) is one of the relevant parameters. It measures, in dB, how quickly perceived speech volume falls as a function of distance from the sound source.

•    In other spaces with many noise sources, such as call centres and restaurants, the main requirement is simply lowering the noise level. Here, requirements may be stated in terms of sound strength (G), which measures, in dB, how much the room contributes to the lowering of the noise level.

An acoustic strategy that encompasses these considerations can help to create better environments that have a sound effect on people.  

Spotlight on ceilings
What acoustic ceiling options are available in the market?

–    Lay-in ceilings
o    The most effective and often the most cost effective way to treat room acoustics is with a wall-to-wall lay-in ceiling. The numerous options with regards to size, proportion, ceiling tile edge profiles, colours and integration of lighting and other services means that lay-in ceilings don’t need to be boring ceiling surfaces.
–    Free-hanging units (vertical and horizontal installations)
o    These systems are useful where a wall-to-wall ceiling is not possible or preferred, for example where exposed services or an industrial aesthetic is created. Free hanging units are also useful in retrofit scenarios as they can be installed around existing system or services.

Caption: A training room with acoustic wall panels and ceilings to create an environment with good speech clarity and prevents sound from travelling to the rest of the open-plan office.
Photo by Bartosz Makowski
Courtesy of Ecophon Saint-Gobain

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