The Book of Acoustics

Chapter 4.0 Treatment placement

4.2 Placement by room shape

The geometry of a room shapes the acoustic environment

The shapes created by the location of constructed walls and barriers also form the acoustic character of a space. As these diagrams illustrate, convex and elaborate surfaces cause sound to scatter, flat surfaces cause sound to reflect, and concave surfaces tend to focus sound waves as they reflect away. Collectively, the surfaces of a given space not only influence how sound will behave but also the path that it will take.

If you are in the position to influence the architectural layout of a space, you can make decisions early on that lead to optimal acoustics instead of having to fix problems later. Generally, domes and round shapes should be avoided when possible as they cause sound focusing issues. Parallel surfaces are also problematic, leading to excessive reflection issues such as flutter echos.

Hallways

Hallways have narrow, parallel surfaces that cause echos due to sound bouncing back and forth. The fact that hallways are often high traffic areas can make noise especially problematic.

Strategy: Add sound absorbers on the walls at shoulder height or higher. Add rugs or carpeting to the floor.

Sound absorbers must be placed as close to the sound source as possible. Therefore, the absorbing materials must primarily be placed on the walls.

Small spaces

Short wall-to-wall distances in smaller rooms cause echos as sound bounces back and forth between parallel surfaces.

Strategy: Place sound absorbers at reflection points on walls and ceiling.

Sound absorbers with a low-frequency profile should be used and placed on the ceiling surface.

Large spaces

In larger spaces, reverberation time increases and sounds can be heard over long distances.

Strategy: Use wall and ceiling treatments and barriers that diffuse and absorb sound.

With low ceiling
Sound absorbing and sound diffusing materials should be used, and sound barriers should be applied to the ceiling. The sound regulation from the floor is secured by furniture and the use of sound barriers.

With high ceiling
The sound level should be reduced in such a way that some of the sound masking effect from the relevant noise is still present. Furthermore, the spreading of sound should be limited.

Circular Spaces

Round or domed spaces cause sound to move towards the centre of the room, causing excessive focusing and echos.

Strategy: Place sound diffusers along the curved surfaces of the space.

Round rooms
The sound diffusing elements should be placed on the curved surfaces in order for the sound to be dispersed in many directions. The working stations should not be placed in the centre of the construction. In stead, furniture with sound diffusing properties should be placed in the centre.

Domes
The sound diffusing elements should be placed on the curved surfaces in order for the sound to be dispersed in many directions. The working stations should not be placed in the centre of the construction. In stead, furniture with sound diffusing properties should be placed in the centre.

Slantered Spaces

Slanted or inclined surfaces like ceilings or walls cause sound to both spread and become overly concentrated in one area.

Strategy: Add sound absorbing materials to the surface directly opposite to the inclined wall or ceiling.

Inclined ceilings
The wall area opposite the inclined ceiling should also be equipped with sound absorbing materials. As a principal rule, all surfaces above the normal ceiling height (2.60 m) including the end walls should be equipped with sound absorbers.

Inclined walls
The sound spreading effect is achieved by inclining the wall in proportion to other walls and the ceiling. In general, the walls inclined by more than 6 degrees ensure an excellent sound diffusion. The most effective diffusion is obtained by applying several angles.

Connecting rooms

Sound travels from one room to the next and spreads out, causing disruption, diminished speech privacy and a potential echo chamber effect.

Strategy: Add sound absorbers to the upper walls and ceilings of both rooms.

Both rooms must be equipped with sound absorbers. If the distance between the opening and the opposite walls is short (5-6 m), the walls much be covered with sound absorbers or diffusers.

Multi-storey rooms

In multi-storey spaces, sound travels between areas causing excess noise and diminished speech privacy.

Strategy: Cover all surfaces in sound absorbing or diffusing materials, possibly including vertical absorbing or blocking barriers.

Both rooms must be equipped with sound absorbers. If the distance between the opening and the opposite walls is short (5-6 m), the walls much be covered with sound absorbers or diffusers.

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The Book of Acoustics

This is a handbook for architects and interior designers who want to create acoustically beautiful spaces that make people feel happier, healthier and more productive.

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