Research On The Pneumatic Through-Hole Silencer And The Acoustical Material

Exhaust noise is produced when pneumatic system works. The noise wouldinfluence the system’s age and efficient as well as people’s health. Silencers canbe used to control the exhaust noise. However, the most common silencers haveenclosed structure, which would produce pressure drop and influence the systemworking. This research proposes using through-hole silencers, which would solvethe problem. In this study, the acoustic material used in through-hole silencer isthe main object.The common acoustic materials are classified, eight different materials arechosen in this study, including four polyester fibre with different density, galssfibre, metal fibre, rock wool and cotton. Materials’ density, thickness, resistivity,porosity, structure factor, viscosity characteristic length and thermalcharacteristic length are chosen as the characteristic parameters based on thesound absorbing theory. Eight materials’ characteristic parameters are testedthrough experimernt.Eight materials’ acoustic impedance and absorption coefficient arecalculated by improved Johnson-Allard equivalent fluid model and theircharacteristic parameters. The characteristic parameters’ influence is alsocalculated by improved Johnson-Allard equivalent fluid model. The result canhelp choose acoustic materials’ for different frequency’s noise.Eight materials’practical ability is experimented by standing wave pipe method. Their actualacoustic impedance and absorption coefficient is tested.All the silencers with eight different acoustic materials are studied by finiteelement analysis and experiment. Using an FEA sofeware Virtual Lab calculatedsilencers transmission loss. All the produced silencers are installed in the system.Their working conditions are experimented and the noises are spectral analyzed.In this study four different kinds of acoustic materials are studied. Theresearch shows that high molecular synthetic materials such as polyester fibre fitthrough-hole silencers the best. Inorganic fiber materials such as glass fiber fitworse. Metal fiber fits mideum and low frequency band. Organic fiber such ascotton and rock wool don’t work well for through-hole silencers.