The theoretical studies previously made on the filtration of compressional waves in solid rods by Lindsay and White have been extended to the case of torsional waves in a rod and of compressional waves in rods having solid rods for side branches. If an infinite cylindrical rod is loaded at equal intervals of length 2lwith disks (having planes perpendicular to the rod) of massmand moment of inertiaIabout the axis of the rod, the resulting structure is found to act as a low‐pass filter for torsional waves. The transmission bands are given by the condition+1⩾cos W⩾−1, wherecos W = cos 2kl − ωI/πa4ρ0c⋅sin 2kl. Herek = ω/c = 2πν/c, where ν is the frequency of the waves. The velocity of propagationc = (μ/ρ0)12, where μ = rigidity modulus and ρ0is the mean density of the rod. The radius of the rod isa. For givenI, increase inldecreases both the cut‐off frequency of the first transmission band as well as the upper limit of the first attenuation band. For givenl, increase inIdecreases the cut‐off frequency. There is next considered the case of an infinite cylindrical rod loaded at equal intervals of length 2lwith perpendicular side rods of lengthls. The approximate assumption is made that longitudinal compressional waves in the main rod set up transverse flexural waves in the side rods. Calculation indicates that if the side rods havefreeends the structure acts as a low‐pass filter for compressional waves in the main rod. If on the other hand the side rods have rigidly clamped ends, the structure under suitable choice of dimensions (in particularl/ls≫1) can act as a high‐pass filter. Numerical illustrations are given.