Sound Insulation Principle of Raised Floor System: How Can Access Floor Reduce Noise and Soundproof?

With a raised floor, panels and a floor finishing coating are laid on a load-bearing structure on top of a solid or light floor. A vacuum is thus created between the material and the raised floor. The lightweight design and technical void, accommodating conduits and pipelines, provide flexibility and insulation against airborne and impact noise. 

A raised floor can be placed on a light or solid load-bearing floor. Generally, raised floors are avoided for acoustical reasons. However, they also influence the acoustics by greatly improving the direct insulation against airborne and impact noise between two superimposed rooms.

What is The Sound Insulation Principle of Raised Floor System?

A raised access floor mainly influences airborne and impact sound insulation in three ways:

• Direct transmission to the premises of the lower floor,

• Aerial transmission of footsteps to the adjacent room via the void below the raised floor,

• Structural transmission to the adjacent room via the floor slabs.

Airborne Sound Insulation of Raised Access Floor

1. Direct sound transmission to the below rooms

The raised floor acts as a counter-partition for the load-bearing floor according to the mass-spring-mass principle, thus improving airborne sound insulation. As for a counter partition, this improvement is defined by:

• The existing load-bearing floor slab,

• The supporting structure (whether or not there is an anti-vibration material between the two),

• The quality and quantity of contacts,

• The height of the void,

• The material type of filling of the raised floor panel if there is one.

The sound insulation can be limited to the level of the low frequencies and the resonant frequency of the mass-spring-mass system. The higher the raised floor and the heavier the plates, the lower this resonant frequency will be.

2. Sound transmission by vacuum under the raised floor to the adjoining room

If the wall rises from the floor of the shell to the ceiling of the shell, this transmission route is non-existent. If the wall is placed on the raised floor, the sound enters a room through the raised floor, then diffuses into the void under the raised floor and is diffused again into the adjacent room through the floor plates. To obtain sufficient acoustic reduction by this route, an acoustic barrier should be provided.

Sound insulation against footsteps is defined by:

• Sound insulation of the panels: the heavier and more flexible they are, the better the sound insulation will be.

• The height of the void under the raised floor: the higher it is, the lower the resonant frequency of the mass-spring-mass system, and therefore the better the sound insulation.

• The sound barrier: the higher the sound insulation of this barrier, the better the sound insulation against traffic noise.

• The presence of pipes or conduits: if the pipes run through the raised floor between two neighboring rooms, the noise will also be transferred through this. An intelligent design of the pipe system avoids this.

3. Structural sound transmission through the floor panels to the adjacent room

If the raised floor is interrupted at the location of the dividing wall between the dwellings, this path does not exist. But this is not always possible, and the coating sometimes passes under a wall separating two rooms. The decoupling of the wall and the raised floor can, in this case, bring an improvement knowing that a side channel is thus eliminated.

Sound insulation will then also be defined by:

• Sound insulation of the panels: the heavier and more flexible they are, the better the sound insulation will be;

• The type of raised floor: a hollow floor will be less effective than panels, because its structure has greater cohesion. In fact, in the case of the raised access panels, the latter not being integral, the vibrations are transmitted to the neighboring panels only by the structure.

Impact Sound Insulation Of Raised Access Floor

1. Direct sound transmission to the below rooms

A raised floor can improve the insulation against contact noise to the room below by about 8 to 20 dB. This improvement also depends on:

• The load-bearing floor slab,

• The supporting structure (with or without anti-vibration material between the two),

• The quality and quantity of contacts,

• The width of the raised floor system,

• The material of the raised floor panel.

2. Sound circulation passing through the void under the raised floor to the next room

The impact sound insulation between two adjacent rooms is influenced by the same elements as the airborne sound insulation (acoustic insulation of the panels, height of the void under the raised floor, the sound barrier, the presence of pipes or conduits) . Below the critical frequency of the panel material, defined by its mass and stiffness (generally approx. 630 Hz to 1000 Hz), this path is decisive.

3. Structural sound transmission through the floor plates to the adjacent room

The impact sound insulation between two adjacent rooms is influenced by the same elements as the airborne sound insulation (acoustic insulation of the panels, type of raised floor). Above the critical frequency of the panel material, defined by its mass and stiffness (generally approx. 630 Hz to 1000 Hz), this transmission path is decisive.The type of flooring also plays a role in impact sound insulation.