"220V AC Cooling Fan" noise in the background noise below 18 dBA measured no echo chamber. Tested fan running in free air, one meter away from the air inlet disposal a noise meter. Fan selection process, but also consider the manufacturer's technical strength, maintenance level of fan service is timely, can ensure the normal use of the cooling fan. In addition, "220V AC Cooling Fan" manufacturers in new product development performance, to reflect the strength of its technology, consideration should also be included in the selection. All need to use the "220V AC Cooling Fan" design engineers electrical and electronic products, must decide on a particular system needed for cooling air flow, and the required amount of wind power depends on the understanding of the system and whether it can take away enough heat , the situation in order to prevent the system from overheating occurs.