acoustic impedance

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Related to acoustic impedances: Sound impedance


1. obstruction or opposition to passage or flow, as of an electric current or other form of energy.
2. the resistance in alternating current circuits, represented by the letter Z in mathematical formulas. Medical equipment is often rated according to impedance to allow for optimum performance by matching impedance ratings. A transformer can be used between components to cause the impedances of unequal systems to match.
acoustic impedance an expression of the opposition to passage of sound waves, being the product of the density of a substance and the velocity of sound in it.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

a·cous·tic im·ped·ance

the resistance that a material offers to the passage of a sound wave (colloquial); a property of a medium computed as the product of density and sound propagation speed (characteristic acoustic impedance). Discontinuities in acoustic impedance are responsible for the echoes on which ultrasound imaging is based. Unit: the rayl.
Farlex Partner Medical Dictionary © Farlex 2012

a·cous·tic im·ped·ance

(ă-kūstik im-pēdăns)
Resistance that a material offers to the passage of a sound wave (colloquial).
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
References in periodicals archive ?
Inspection of dissimilar metal-composite adhesive joint is a complex task, as the acoustic impedances of the adherents differ, meaning that there will be strong reflection at the interface of two dissimilar materials even without defect in it [3]-[5].
The acoustic impedance (in Rayl/[m.sup.2] or ([lb.sub.f]/[ft.sup.2])/([ft.sup.3]/s)) relates the particle velocity ([??]) directed away from the source to the acoustic pressure ([??]) and can be expressed as
The condition of the acoustic microscopic analysis is the difference between the acoustic impedance of the materials.
1, we applied the transfer matrix formalism combined with the annealing algorithm to design the optimum arrangement of 6 layers with different lengths and acoustic impedances. The experimental data were plotted in the domain 20 Hz-200 Hz.
It is here noted that the amount of seismic energy transmitted or refracted in the earth is influenced by the acoustic impedance contrast between the lithologic bed boundary.
As a longitudinal wave normally travels from medium 1 to medium 2 with acoustic impedances [Z.sub.1] = [[rho].sub.1][V.sub.1] and [Z.sub.2] = [[rho].sub.2][V.sub.2], respectively, the wave is partially reflected and partly transmitted.
If, during its real-world application the AET measures, the wave of other type that propagates in a material with substantially different acoustic impedance, then the transducer characteristics obtained during calibration are not comprehensive enough.
Goran, "Influence of ultrasonic transducer acoustic impedances and dimensions on its input electrical impedance," Working and Living Environmental Protection, vol.
This is caused by the higher acoustic impedance in sclerotic bone since acoustic impedance is directly related to density that increases in sclerosis [20].
The electromechanical coupling coefficient, kt, in the thickness direction, along with other characteristics, such as the mechanical quality factor, [Q.sub.m], and acoustic impedance, [Z.sub.a], have been found from measurements on the electrical impedance of the piezoelectric composites.
It can be incorporated into a surface mounted AE sensor (5), where the electroactive composite is adhered to a backing material of the same acoustic impedance and electrical contacts are made to both faces, or be embedded into a fiber reinforced epoxy laminate structure (6).
For the case of identical materials (of the acoustic impedance Z) on both sides of the gap and the gap distance, d, being much less than V/2[pi]f (V is the wave speed), or d << V/2[pi]f, we have an approximate expression for T from Krautkramer [7] as