TIP: Akustikabsorber® & Vibrabsorber®+Sylomer good practices to achieve noise and vibration isolation whilst maintaining correct engine cooling performance.

Akustikabsorber® noise attenuating composites are often installed in industrial machinery to absorb, insulate and damp airborne noise.

VIbrabsorber+Sylomer ® spring vibration isolators are often installed beneath industrial machinery to isolate structural noise.

When it concerns airborne noise insulation, the installation principle consists of encapsulating the machine as shown in the figure below.

Fig 1: General overview of encapsulation within a Noise and vibration generating machine.

In order to achieve the optimum results the below advices should be followed:

1. Install the machine on the stiffest part of the frame.

2. Place the machine on vibration isolators that provide vibration isolation following a calculation, according to the percentage of isolation that is required. More information click here.

3. It is recommended to use belts or roller drive systems which provide less noise than gear trains. Rigid piping and stiff wiring can act as an acoustic bridge, therefore use flexible hoses and wiring instead.

4. Apply vibration damping materials which have high load and viscosity. Rubber plates such as MP-5 / MP-10 can be placed on the surfaces exposed to the greatest vibration, this will help to reduce noise.

5. Install an Akustikabsorber that provides the highest transmission loss and absorption coefficient to reduce noise build-up inside machine.

6. Avoid all mechanical contact between the cabinet and the machine chassis, as this can act like as an acoustic bridge.

7. Seal openings at the base and other parts of the cabinet to prevent noise leakage. In fact, when a sound wave encounters an obstacle or an opening which is comparable in size to its wavelength, the sound will bend around the obstacle or squeeze through the opening with little loss of energy, as shown below. The amount of sound energy that passes through a small hole or hairline crack in a wall is far greater than one would predict based on the size of the crack. This points out how important it is to caulk or seal all cracks or openings in walls, doors, etc., which separate areas where privacy is desired.

Fig 2: Diffraction of noise when passing a small hole of a wall.

HOW TO CONTROL SOUND DIFFRACTION WHILE ALLOWING THE CORRECT ENGINE COOLING PERFORMANCE.

The cooling system serves three important functions. First, it removes excess heat from the engine; second, it maintains the engine operating temperature where it works most efficiently; and finally, it brings the engine up to the right operating temperature as quickly as possible.

When the transfer of thermal energy occurs via heat conduction, a thermal flow is required, this is to say an entrance of cold air and an extraction of hot air. For this purpose, forced ventilation with axial fans may be required.

Since noise diffraction can occur through a hole where an axial fan is placed, it is advisable to follow some advice, so noise insulation is achieved whilst hot air is extracted.

Fig 3: General overview of an encapsulated machine with a cooling flow of air.

Additionally to the advice given in Fig 1 the below advice can be also useful for those installations where cooling and noise insulation is required.

1. Any entry and exit holes created for ventilation should be covered with Akustikabsorber® materials that provide good transmission loss and absorption coefficient.

2. Applying vibration damping materials which have high load and viscosity. Rubber plates such as MP-5 / MP-10 should be placed on the surfaces exposed to the greatest vibration, this will avoid metallic plates responding to vibration and generating noise.

3. Position the air inlet/outlet to an area/direction which is outside humans hearing presence. Ideally outlets should be pointing upwards to an area which has a large air volume.

4. Install vibration isolators to suspend the axial fan , this avoids radiation of structural noise and secondary airborne noise.

5. Seal openings at the base and other parts of the cabinet to prevent noise leakage.

6. Solid constructions which are generous in mass (concrete/metal) provide better results than light construction structures (wood/plastic).

7. Install double walls covered with Akustikabsorber® materials for optimum sound insulation.

Do not hesitate to contact our technical department if you require help on this topic.