Air Piston compressor is a reciprocating machine that uses crack shaft mechanism to compress air. Usually this type of machine is quite noisy, typical noisy level are around 95[dB]. This project is meant to look for noise sources and study a strategy to reduce the sound emitted. Thesis work was developed thanks to technical support and resources of Atlas Copco group, company leader in air compressor technique. One of the last machines designed in Atlas is Pat due machine, it will be the subject studied thought this research. This paper is meant to study the fluid dynamic noise source at compressor inlet, a new inlet filter concept will be designed according to fluid dynamics laws and tested.