Sound insulation describes how much sound is reduced when it is going through a structure. Buildings have two types of sound insulation: airborne and impact.
Use airborne sound insulation when sound produced directly to the air is insulated. Determine the amount needed using the sound reduction index Rw or R`w. The greater the Rw value, the better the insulation. The values should be corrected (C and Ctr) in case of additional special noises in the surrounding environment.
Rw + C for noise such as:
- Living activities
- Noise from high-speed trains
- Industrial noise (medium and high frequency)
Rw + Ctr for noise such as:
- Street noise
- Noise from low-speed trains
- Disco music
- Industrial noise (low and medium frequency)
The lowest sound insulation demands can be passed with a single-layer wall. If the wall mass is doubled, the sound reduction figure increases to around 6 dB. The sound is absorbed by the insulation.
Sound insulation of low frequencies demands more mass. To get more mass, use a double-layer wall. The most effective way to increase the mass is to add several thin plaster board layers top of each other. Put insulation in the cavities to improve sound insulation. Insulation in a wall improves sound insulation by 5 – 10 dB compared to a wall without it.
B) Floating floors
Use impact sound insulation (or step sound insulation) for floating floors. Determine the amount needed by the sound pressure level in the adjacent room below. National regulations usually stipulate the ”highest level of floor impact sound”. A low Ln or L’n signifies a good level of floor impact sound insulation. Ln and L’n is measured in a frequency range of 50 – 5000 Hz. Ln is measured in the lab, while L’n is measured in the field.
PAROC stone wool has excellent properties for the resilient layer in floating floors. It is hard enough to bear the load from the upper layer (floor deck) and soft enough to effectively reduce the vibrations between the construction layers in the floor. The most important property for insulation material is called dynamic stiffness expressed in MN/m3. The lower the dynamic stiffness for the PAROC product, the better impact sound insulation it contributes.
Wooden structures are very hard to improve. The connections are stiff and they have low structural weight. Consider every single situation separately.
An intermediate floor made of concrete already has relatively good airborne sound insulation. The new demands for impact sound insulation, however, make concrete an increasingly common choice for floating floors.
More information about floating floors and their sound insulation values can be found here