acoustic impedance

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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 ?
Due to their relative softness and low acoustic impedance, at high strain rates the applied strain field may not be uniform.
The elastic impedance allowed to calibrate far offset angle stack like acoustic impedance logs are used to calibrate zero-offset data.
At this frequency, acoustic impedance is equal to zero which means the sound wave is by-passed and the effective bulk modulus is also zero.
where AI is the acoustic impedance of the material and D and V are the density and velocity of the material, respectively.
Caption: Figure 5: Variation of acoustic impedance with concentration at 35[degrees] C temperature.
A material that has an acoustic impedance of 6.0 at 15 MHz will have the same acoustic impedance when a 230-MHz transducer is used.
Detection of non-wet scaffold parts can be performed the most objectively and precisely because of the meaningful difference between the acoustic impedance of the polymer media and air bubbles.
The following tests were performed during a non-infectious period: pure-tone audiometry, acoustic impedance, otoacoustic emission, and brainstem audiometry.
In this section, the influences of the tortuosity fractal dimension and the pore area fractal dimension on the specific surface acoustic impedance [Z.sub.s]/[Z.sub.0], the complex wave number k, and the sound absorption coefficient a are presented and discussed.
Assume that there is a rigid pipe with two variational cross sections, of which the acoustic impedance changes from [Z.sub.1] to [Z.sub.2], as is shown in Figure 4(a).
The reflected signals were used to calculate the acoustic impedance of the anterior and posterior segment of the cornea, which were based on reflection and transmission coefficient models established by continuous monitoring of stress and strain.
A possible cause of honey's higher response is its higher acoustic impedance, Z.