Structure-borne sound arises when mechanical oscillations cause a surface or construction to vibrate. These vibrations travel through the material and may cause components and materials to oscillate and emit unwanted noise into their surroundings.
A common example is in light or heavy vehicles, where vibrations from the engine, fan or other vehicle parts are transmitted through the chassis and bodywork.
The driver and passengers may perceive a dull noise or a resonance, even if the sound source is not directly audible in the air.
By damping the vibration, the noise is reduced, which may otherwise need to be addressed with sound-absorbing materials.
The ability to dampen structure-borne sound can be described using the so-called acoustic loss factor (η) (damping factor). This indicates how much of the vibrational energy in a material – for example, a steel sheet – is converted into heat rather than continuing to spread as vibrations or sound.
A high damping factor reduces the vibration level in a structure and, as a result, the radiated noise. An undamped steel structure typically has a loss factor between 0.001 and 0.01. The highest theoretically possible loss factor is 1.0, but a structure-borne sound damping material is considered effective if the loss factor exceeds 0.1.
Structure-borne sound can be reduced by minimising vibrations or preventing them from propagating through the construction.
By using damping materials with a high acoustic loss factor, part of the vibrational energy is converted into heat instead of spreading further as sound. With correct placement, for example in body parts, engine mounts or floor structures, vibrations caused by structure-borne sound can be drastically reduced.
Antiphon offers a range of solutions for the reduction of structure-borne sound.
antiphon® MPM™ is a structure-borne sound damping laminate sheet featuring a viscoelastic layer between two metal sheets. This construction effectively dampens vibrations and, consequently, the propagation of structure-borne sound. The laminate sheet replaces conventional sheet metal without significantly increasing weight.
Antiphon also offers structure-borne sound damping pads. These pads are applied directly to metal or plastic surfaces and convert vibrational energy into heat.
Together, these solutions help to effectively reduce vibrations and create quieter constructions in vehicles and other environments where structure-borne sound is an issue.
