DEMONSTRATION OF DAMPING THANKS TO HEAVY MASS
INTRODUCTION
Have you ever wondered about the use of heavy masses in order to dampen vibration? At AMC we have carried out a small experiment with the help of a percussion instrument called a Gong to demonstrate the effects.
The aim of the experiment is to study the acoustic differences between hitting the free Gong and comparing it if we add different sizes of heavy mass elastomer in the center of the instrument as you can see in the following image.
TEST
It is a small Gong of 12.5cm in diameter. To attenuate the noise, 3 rings of different sizes of our heavy weight MP5 A with a thickness of 2mm have been installed in the center of the Gong. The objects under study are presented below.
| Gong without Heavy Mass MP5 A |
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MP5 A - 1
Øext: 3cm Øint: 1,5cm |
MP5 A - 2
Øext: 6cm Øint: 4.5cm |
MP5 A - 3
Øext: 9cm Øint: 7,5cm |
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Gong with Heavy Mass
MP5 A (1) |
Gong with Heavy Mass
MP5 A (1 + 2) |
Gong with Heavy Mass
MP5 A (1 + 2 + 3) |
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To better understand the object to be analyzed, we have first carried out a finite element study with our FEM software to understand the vibratory modes of the Gong. According to this study, the vibratory mode with the highest energy is at 1084Hz.
| Vibration mode - 1084.2Hz | Vibration Mode Animation |
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This vibratory mode at 1084Hz obtained by the FEA study agrees with the spectrum of noise that we have measured when hitting the Gong. It can be seen that when we hit the instrument (at second two on the graph), the mode with the highest energy appears at levels close to the theoretical vibratory mode.
| Gong noise spectrum |
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To compare both cases, we have made a temporary measurement in dB A hitting the Gong in second 2.
| Temporal measurement in dB A |
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As can be seen, thanks to the first small heavy mass added to the Gong we are able to reduce noise by 10 dBA. However, as we add more heavy mass to the system the decrease is more significant, reducing by 20 dBA with the three heavy mass layers. The heavy mass works as a vibration damper, considerably reducing its vibratory amplitude, thus reducing noise.
TRIAL VIDEO
The AMC heavy mass layers are available in sheets up to 1230 x 1030mm and in either 2.6mm or 5mm thickness. They have a density of 1950 kg/m3 and can be supplied with a self-adhesive backing on either a single or both sides. More information on this product can be found on our website through this link.
AMC MECANOCAUCHO manufactures anti vibration mounts and has a team of application engineers to help your installation needs so do not hesitate to contact our technical department if you require help on this topic.
