The theoretical treatment of acoustic absorption which goes as a power of the frequency is quite subtle. In this paper, it is shown that some of the difficulties can be resolved by using a wide distribution of relaxation times which is cut off at a short time limit 1 Ͼ0, and a finite long time limit 2 Ͻϱ, without altering the general form of the acoustic response. This formalism is used to show that quadratic, linear, and fractional losses can be consistent with the Kramers-Kronig ͑KK͒ causal relations. The linear loss in polymers is associated with a weak velocity dispersion, so the group velocity and the phase velocity are quite close. The implications for space charge measurements in insulating polymers are discussed. Using the Helmholtz-Kirchhoff tube absorption as an example, it is also shown that the local approximation for the KK relations is unsatisfactory.