This paper presents a theoretical study of the acoustic dispersion in media containing many spherical scatterers. The existing dispersion relation is used to investigate the dispersion in media containing particles such as low acoustic-contrast fluid, rigid and elastic spheres, as well as air bubbles. It is shown that in the case of low acoustic-contrast fluid, rigid and elastic spheres, the presence of scatterers has more profound effects on the acoustic attenuation than on the phase speed, whereas in the bubble case, both the attenuation and phase speed can be affected significantly. Then the dispersion relation is examined via the Kramers-Kronig relations, as they express a general identity for dispersion and are therefore ideal to test the suitability of a specific model for acoustic propagation. Results indicate that although there remain some discrepancies, the existing dispersion relation satisfies the Kramers-Kronig relations reasonably well. Good agreement is particularly apparent in the bubble case. Possible cause for the discrepancies is also discussed in connection with a discussion of the assumptions that lead to the dispersion relation. (C) 1997 Acoustical Society of America.
