Airborne sound insulation

Which problems do we find when we want to improve the airborne sound insulation of some enclosure, Wall, Floor or Ceiling?

The biggest problem is the ignorance!

Adding mass to a partition will homogeneously increase in the insulation, but in which frequencies? Are all frequencies of our interest?
These are the big questions that we must answer.

Insulation of double and single leaf partitions

The specific insulation of a wall, depends on its superficial mass, its stiffness decoupling, intrinsic damping and sealing. 3 different regions can be considered depending on its behaviour:

REGION 1: Elasticity Zone

It is defined by the resonance frequency (fr), the natural frequency of vibration of a partition, known as the “drum effect”. The fr depends on several factors, such superficial density (mass per unit of area), size, contour conditions, flanks, stiffness of intermedium layers and flexural stiffness. The main concern is lowering this frequency shifting it out of the interest frequencies (audible range).

REGION 2: Mass Zone

The insulation is defined by the mass of the system. For each increase in mass, the insulation increases at a pace of 6 dB for each double mass and frequency. Is relatively simple to increase insulation in this zone by simply adding heavier elements, trying not to make the whole system nor excessively heavy nor expensive.

REGION 3: Damping Zone

In this zone insulation is defined by the critical frequency. This is the frequency at which flexion waves c_f match the speed of sound in the air. From this frequency on the insulation increases at a higher pace than mass zone (10dB/octave). However, it generates an important decrease in the insulation at the exact frequency. The frequency range improves when several layers are joint together with different critical frequencies.

Generating a cavity, thanks to the decoupling effect, will result in an improvement of the insulation in medium and high frequencies. However, it will also create the resonance phenomenon, only present in double leaf walls.

IDEAL SOLUTION: Elastic heavy mass elements

The ideal solution must provide mass and elasticity between two rigid boards, dissipating energy by viscosity. It should transform the curve into more linear one, diminishing the resonances that appear in the curve which decrease the insulation. It should shift the resonance frequency out of our frequencies of interest (audible range) and displace coincidence frequency towards high frequencies. So the generated lack of insulation should be diminished. It is important to install it with the least number of points of connection.

dBsonic HM-3D, is the only acoustic membrane on the market designed to be used like a sound blocker. The external latex layers diminish the rigid connection between elements and create a flexible layer between two rigid ones. It will decrease the dynamic stiffness of the assembly system. Improves the area dominated by the mass law by adding 5 kg/m² with flexible nominal mass in the whole surface of the wall at the same time, preventing a coupling of incident wavelength with the coincidence wavelength of the partition.

The installation of this fantastic membrane improves any multiple insulation system, by adding the following advantages: