Our focus presently is only the four types: Open, enclosed, silent and ultra or super silent. Before we begin in the descriptions of these sound levels we also need to know the following: 3,000 rpm and 1500 rpm gen sets. Speed rpm (revolutions per minute) represent the speed at which the engine is turning, like on a motor vehicle rpm when the engine is idling, it normally idles at 600 rpm and some vehicles can revs up to 10,000 rpms, generators is only 2 speeds, 3,000 rpms and 1500 rpms where speed of a generator determine the cycles of power in Hz, and must be as close as posable to 50 hz In South Africa. Therefore we can say that 3000 rpm only consist of two Poles and 1500 rpm generators consists of a 4 poles alternator, both will generate 50 hz power.
Now back to noise levels, the faster the engine turns, the more louder the noise, even enclosed sets at 3,000 rpm is not really silent, these engines is actually classified as semi silent, so we will include this also to our category. We will start out with the loudest types gen sets. Open set 3000 rpm 125 db petrol or diesel. These generator sets are principally the noisiest, as it is typically an air cooled petrol or diesel generator normally at around 125 decibels (DB.). It is compact and also not heavy as this design can utilize more compact engines to obtain the similar power at high speeds, as on low speed generators (1500 rpm). Plus, these generators can purely be used for limited periods of time as it is designed solely for standby use.
Semi-Silent (enclosed) 3000 rpm 95 db petrol or diesel. These generator sets is the same builds as the open set 3,000 rpm, except that it is enclosed. The engine and alternator are build into the enclosure and normally also insulated with a larger more silent exhaust system. Also designed for standby use, it is a more expensive than the Open Set 3000 rpm units. These generators can be operated at houses but not in lifestyle estates as the sound level is still high and estates require a decibel range at 60 db or lower.
Open Set 1500 Rpm 70 to 95 db diesel. Typically depending on the engine type, these generators can also be silent from 70 to 95 decibels. This is typically justified to the fact of the different fuel systems and injection types. These generator sets are typically diesel fuel. Open set generators typically consist of a frame where the engine and alternator is mounted upon. It can be operated inside a generator room or can be placed under an external space covered with a roof to preserve it from direct sun and rain.