Abstract
In this paper, a silencing unit was developed for reducing noise radiated from the cooling systems of OA-equipments or measuring instruments. It was proved by model experiments that a silencing rectangular bend with rather thin sound absorbing material for high frequency and acoustically transparent walls for low frequency is compact and has high noise reducing performance. They can reduce the radiate noise by about 7dB in the studied example. The noise reducing mechanism of acoustically transparent walls is considered to be that the acoustic energy radiated into a silencing rectangular bend and reflected from the duct exit passes through the acoustically transparent walls into a box and dispersed and absorbed by some electrical plates in the box.
