Nondissipative side‐branch acoustic filters for liquid piping systems are discussed in this report. Simple spring‐mass resonators are used as branch elements. The filters are analyzed as lumped‐parameter systems for short pipe lengths and as distributed‐parameter system for long lengths. One‐, two‐, and three‐section filters are treated and results of tests under both flow and no‐flow conditions are given. Band rejection characteristics are obtained with attenuations up to 40 db for no liquid flow. Under turbulent flow conditions effective attenuation is found to be reduced by noise regeneration.