Acoustic contrast factor

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The acoustic contrast factor is a number used to describe the relationship between the densities and the sound velocities (or, equivalently because of the form of the expression, the densities and compressibilities) of two media. It is most often used in the context of biomedical ultrasonic imaging techniques using acoustic contrast agents and in the field of ultrasonic manipulation of particles much smaller than the wavelength using ultrasonic standing waves. In the latter context, the acoustic contrast factor is the number which, depending on its sign, tells whether a given type of particle in a given medium will be attracted to the pressure nodes or anti-nodes.

Example - particle in a medium[edit]

Given the compressibilities and and densities and of the medium and particle, respectively, the acoustic contrast factor can be expressed as

For a positive value of , the particles will be attracted to the pressure nodes, and vice versa.

See also[edit]