In contrast, it is widely noted that the frequency dependent exponent η {\displaystyle \eta } of viscoelastic materials is between 0 and 2.[1][2][3][11][12] For example, the exponent η {\displaystyle \eta } of sediment, soil and rock is about 1, and the exponent η {\displaystyle \eta } of most soft tissues is between 1 and 2.[7][8][10][11][12]