Ultrasound attenuation spectroscopy
Encyclopedia
Ultrasound attenuation spectroscopy is a method for characterizing properties of fluids and dispersed particles. It is also known as acoustic spectroscopy
There is an international standard for this method.
Measurement of attenuation coefficient
versus ultrasound frequency
yields raw data for further calculation of various system properties. Such raw data are often used in the calculation of the particle size distribution
in heterogeneous systems such as emulsion
s and colloid
s. In the case of acoustic rheometer
s, the raw data are converted into extensional viscosity
or volume viscosity
.
Instruments that employ ultrasound attenuation spectroscopy are referred to as Acoustic spectrometers.
There is an international standard for this method.
Measurement of attenuation coefficient
Attenuation coefficient
The attenuation coefficient is a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles, or other energy or matter. A large attenuation coefficient means that the beam is quickly "attenuated" as it passes through the medium, and a small...
versus ultrasound frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
yields raw data for further calculation of various system properties. Such raw data are often used in the calculation of the particle size distribution
Particle size distribution
The particle-size distribution of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amounts of particles present, sorted according to size...
in heterogeneous systems such as emulsion
Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...
s and colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
s. In the case of acoustic rheometer
Acoustic rheometer
An acoustic rheometer employs piezo-electric crystal that can easily launch a successive wave of extensions and contractions into the fluid. It applies an oscillating extensional stress to the system...
s, the raw data are converted into extensional viscosity
Extensional viscosity
Extensional viscosity is a viscosity coefficient when applied stress is extensional stress.Extensional viscosity can be measured using rheometers that apply extensional stress...
or volume viscosity
Volume viscosity
Volume viscosity becomes important only for such effects where fluid compressibility is essential. Examples would include shock waves and sound propagation...
.
Instruments that employ ultrasound attenuation spectroscopy are referred to as Acoustic spectrometers.