SOUND ABSORBING

Best known for its waterproofing capabilities, Bitumen has also proven to be particularly effective for sound absorption, as Bitumen is a viscoelastic material, which means that it has the capacity to absorb sound by transforming vibration into heat. Bitumen reduces the transmission of vibrations caused by external sources. That’s why bitumen is also used as a heavy mass around car engines and in washing machines, among other, as a soundproof material.

To sum up the advantages of using bitumen for sound absorption are:

• A unique combination of properties: bitumen exhibits viscoelastic behaviour due to its ability to combine both viscous (dissipative) and elastic (restorative) properties when subjected to mechanical stress. This characteristic enables bitumen to absorb and dissipate mechanical energy, including vibrations, which contributes to its damping capacity. 
• Damping of vibrations: viscoelastic materials are excellent at damping vibrations and converting mechanical energy into heat. When sound waves propagate through these materials, the vibrations are quickly dissipated, reducing the amplitude of the waves and preventing them from reflecting back into the environment.

As a viscoelastic material, exhibits good damping vibrations capacity due to its combined viscosity and elasticity. The material's ability to dissipate mechanical energy through internal friction makes it effective at attenuating vibrations and absorbing sound energy. This property has practical implications in various fields, contributing to sound absorption, noise reduction, and improved acoustic environments. 

For impact noise, the measurement parameter used is the impact sound pressure level reduction index, which is indicated as ∆Lw (dB) and represents the improvement introduced by an ONDULINE® sheet. For comparison purpose, a metal roofing sheet (thickness of 3 mm – ribbed profile) has been compared to an ONDULINE® CLASSIC sheet on simulated roof settings and rainfall conditions (Test Report BBTA3.TR.20.00023.R).

• The metal sheet generates 83,09 dB(A) where the ONDULINE® sheet generates 59,88 dB(A): a major difference of 23 dB(A) and a very good performance for a roofing material of only 3 mm! 
• Noise measurement was performed, at constant rainfall, using five microphones inside the rooms. 
• The switch from 60 to 83 is a major difference. Below 60 dB(A), we can have a normal conversation, whereas it becomes really disturbing to overpass 80 dB (A). For example, 80 dB(A) is the level of a high traffic street or klaxons, a garbage disposal or a piano practice.

We can clearly hear the difference between the metal sheet and the ONDULINE® sheet! 

Reducing from 83 dB(A) to less than 60 dB(A) is life-changing. It means that with ONDULINE®, the indoor environment is 4 times quieter than with a metal roof. Thanks to its unique composite material, ONDULINE® roofing generates less noise under rainfall. This reduction of noise has been officially tested by an independent third-party laboratory, the BPPT (Indonesian National Laboratory for Aerodynamics, Aeroplastics, and Aeroacoustics technology), and measured according to ISO 140-18:2006.