Absorption of Sound Arising from the Presence of Intact Cells in Blood

The absorption of sound in blood occurs primarily on a molecular level and is related to the presence of protein in the cells and plasma. However, a small contribution to the total absorption arises simply from the presence of intact cells in the blood. Analysis based on Epstein's theory of scattering shows that the cellular absorption results from a viscous interaction between the fluid and cells when the latter, because of their greater density, fail to follow the oscillatory motion set up by the sound wave.