... LIONGOAL Roots Blower 1, Long life span, Low noise 2, Low-maintenance, Easy installation 3, Enery ... -saving 4, Cast iron Features:i, Low noise with adoption of helical tri-lobe roots rotors and ... the discharge port of special geometry, the airflow noise is much lower compared to typical straight-lobe ... . The noise level can be reduced by 8db in the band of low frequency; hence the noise in the surroundings ...