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Having made an excellent NA Engine manifold, the next step was to make a
silencer with a good noise reduction and a low back pressure.
At the Danish Technical University I found a PHD study from 1970.
In this there were descriptions of silencer systems for the city buses.
The guy had achieved an excellent noise reduction and improved fuel
economy of more than 10%.
It consisted of multiple offset resonances (organ pipe) chambers
(low pass filters). And no damping materials was involved. |
