The attenuation of low‐frequency (≈︁ 103 Hz) sound vibrations and the elastic modulus dispersion in mono‐ and polycrystalline niobium hydrides with hydrogen contents H/Nb ≈︁ 0.8 are investigated over the temperature range from 160 to 450 K. Sound attenuation and elastic modulus dispersion are anomalously high (Q−1 ≈︁ 0.14, ΔG/G0 ≈︁ 0.5) in the region of orthorhombic β‐phase. Such a strong anelastic relaxation is observed only during the motion of Bloch walls in ferromagnets. Such characteristics of the spectrum as a) sharp attenuation decrease outside the β‐phase region; b) a wide range of relaxation times in monocrystalline samples and its narrowing to a single spectral line in polycrystals;; c) a strong dependence of relaxation rate upon hydrogen concentration (sceeding the fourth power) show that the anelastic relaxation in the β‐phase of niobium hydride is caused by domain boundary motion under the action of elastic stresses.

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