plays a significant role in determining acoustic transmission and reflection from the boundary of the connection of two dissimilar materials having different acoustic impedances
The acoustic metric that is most relevant to the combustion oscillation problem is the acoustic impedance
. In fact, the acoustic impedance
upstream and downstream of the flame is used as an input in the feedback loop model developed by Baade (1978, 2004; Baade and Tomarchio, 2008).
The acoustic impedance
is determined by the density p and of the acoustic velocity v of the material (2):
For example, at the boundary of two media with acoustic impedances
[Z.sub.1] and [Z.sub.2] (Cretu & Nita, 2004)
Specifically, at the interface of two formations of contrasting acoustic impedance
, part of the energy will be transmitted across the interface and some will be reflected.
The calculated acoustic impedances
of polymer melt and delay line as well as those of screw root and solid PVC are listed in Table 2 for further attenuation analysis.
The next step is to define the acoustic properties of the acoustic medium and specify the boundary conditions, which are applied as surface velocities, pressures, acoustic impedances
, and simultaneous velocities and acoustic impedances
Considering the shortcomings of the existing calibration equipment, a task to create a portable AET calibration equipment of a new type, with a greater measurement performance and allowing the evaluation of AET characteristics using different wave types and waveguides with different acoustic impedances
, was formulated.
Under the condition that the outer contour surfaces of transducer component parts are loaded by surrounding environment acoustic impedances
, which are small for the unloaded surface, and with alternating voltage applied to the electric inputs, it is possible to determine any transfer function of interest for the given system.
This is most probably explained by the bone sclerosis, in which the bone density increases, thus simultaneously increasing the difference in acoustic impedances
at the cartilage-bone interface.
The acoustic impedances
of the PTCa/epoxy composite systems all show values around 11 MRayls.
In both cases [lambda]/4 layers were used for matching materials with different acoustic impedances
in order to achieve more efficient transmission of the ultrasonic wave through the waveguide-fluid interface .
The composite samples were suspended freely in air and their electrical impedances measured over the frequency range 300 kHz to 50 MHz where the total impedance at resonance is given by the sum of the electrical impedance and the acoustic impedances
Three matching theories exist, namely, energy matching, whole processing matching, and acoustic impedance
A possible cause of honey's higher response is its higher acoustic impedance