The invention provides a noise reducing enclosure for reducing the noise from a vacuum pump, e.g. a roughing pump of a high vacuum system, the vacuum pump having a long axis and the enclosure comprising a noise dampening material and being shaped to radially enclose the vacuum pump along its long axis and being axially open at each end. Airflow is permitted through the enclosure in use and optional integrated cooling means on the pump may assist cooling of the pump. The invention also provides an assembly of the pump and enclosure, a method for reducing the noise from a vacuum pump using the enclosure and a mass spectrometry system comprising: a mass spectrometer having one or more chambers therein which in operation are held under vacuum; and a vacuum pumping system for producing said vacuum, the vacuum pumping system comprising at least one vacuum pump which has a long axis and wherein the mass spectrometry system further comprises a noise reducing enclosure for radially enclosing the vacuum pump along its long axis, wherein the enclosure is axially open at each end.