Sound Reduction with Damping Coating

Damping within the context of damping coating means to reduce resonance by absorption or redirection (reflection or diffusion). Damping can reduce mechanical resonance in the structure of a vessel itself or things in the room. http://en.wikipedia.org/wiki/Soundproofing#Damping

Our damping coating reduces metal structure-based transfer of noise energy and lowers surface acceptance and transmittance to provide decibel reductions of 10-12 dB in the 150-1000 Hz range. That equates to reduction of over half the noise energy. However, on vessel metal structure, low frequency noise energy from engine and mechanical spaces, propeller, bow thrusters and gensets is the most difficult to contain and is the primary target. Noise damping also complements sound barrier and sound absorption materials, reducing noise in addition to their contribution. Additionally, decoupling in the form of absorbent engine, gearbox and genset mountings can contribute substantially to noise control. 

This chart compares damping coating very favorably to "damping tiles", the traditional method for applying dense mass to plate to achieve the same level of vibration reduction as the leading material. The difference between the two methods is the lower cost of spray-applied damping coating and better long term adhesion to the metal surfaces. Additionally, coating weight reduction can be as low as 36 less for comparable results. 

Damping coating yields a 10-12 dB reduction in addition to sound reduction provided by sound barrier (dense mass layer sandwiched between two soft mass layers) and absorbent soft mass.

Performance testing was based on use of the optimal ratio of 25% coating weight to plate weight with application on 70% of surface area between stiffeners. The attached chart shows wet and dry film thicknesses for various aluminum plate weights.
Best performance application surfaces for sound damping would be to apply damping coating on the following surfaces:
  • Machinery/engine space overheads
  • Machinery/engine space forward and aft bulkheads
  • Machinery/engine space sidewalls 
  • If engine stringers are solid mounted - application on both sides. 
  • Engine air intake duct surfaces 
  • Crew quarters boundaries
Secondary damping application areas:
  • Forward chine where waveslap produces noise
  • Machinery/engine space aft bulkhead 
  • Fuel tank vertical face & tops (where exposed)
  • Cabin sole on top of plate

 

 

Damping Coating Application Thickness for Best Results

The chart below advises how much damping coating to apply in terms of wet film thickness (WFT) to achieve a given dry film thickness (DFT). The extensive testing advises that the 25% coating weight to plate weight ratio yields the most cost effective results. Additional 20 mil (0.5 mm) thicknesses typically yielded only a 1 dB additional noise reduction and would be considered too incremental for general application. However, there are circumstances where one can justify the additional cost to achieve specific results for noise reduction.

We apologize for not supporting metric yet. Stay tuned on that!