Published 1988 by National Aeronautics and Space Administration, Langley Research Center in Hampton, Va .
Written in EnglishRead online
|Statement||Michael G. Jones and Tony L. Parrott.|
|Series||NASA technical memorandum -- 100637.|
|Contributions||Parrott, Tony L., Langley Research Center.|
|The Physical Object|
Download Evaluation of a multi-point method for determining acoustic impedance
Evaluation of a multi-point method for determining acoustic impedance. Abstract. An investigation was conducted to develop and explore potential improvements provided by a multi-point method (MPM) over the traditional standing wave method (SWM) and two-microphone method (TMM) for determining acoustic by: An investigation was conducted to develop and explore potential improvements provided by a multi-point method (MPM) over the traditional standing wave method (SWM) and two-microphone method (TMM) for determining acoustic by: The Multi-Point Method (MPM) presented in this report combines the strengths of the Standing Wave Method (SWM) and the Two-Microphone Method (TMM) while avoid- ACOUSTIC IMPEDANCE.
A multipoint method for determining acoustic impedance was evaluated in comparison with the traditional standing wave and two-microphone methods using 30 test samples covering the reflection factor magnitude range Abstract An investigation was conducted to explore potential improvements provided by a Multi-Point Method (MPM) over the Standing Wave Method (SWM) and Two-Microphone Method (TMM) for determining acoustic impedance.
A wave propagation model was developed to model the standing wave pattern in an impedance : Tony L. Parrott and Michael G. Jones. A multipoint method for determining acoustic impedance was evaluated in comparison with the traditional standing wave and two-microphone methods using 30 test samples covering the reflection factor magnitude range Author: Michael G.
Jones and Tony L. Parrott. “Standard test method for impedance and absorption of acoustical materials by the impedance tube method,” ASTM C a. Google Scholar; 9. Jones and T. Parrott, “Evaluation of a multi-point method for determining acoustic impedance,” Mech.
Syst. Signal Process. 3, 15–35 (). Google Scholar; F. by: J. Pope, “Rapid measurement of acoustic impedance using a single microphone in a standing wave tube,” Proc. Paper M ().
Google Scholar; M. Jones and T. Parrott, “Evaluation of a multi-point method for determining acoustic impedance,” Mech. Syst. Signal Proc. 3, 15–35 (). Google Scholar; by: Results from impedance eduction methods developed by NASA Langley Research Center are used throughout the acoustic liner community.
Occasional anomalies persist with these methods at frequencies where the liner produces minimal attenuation. An approach to educe impedance spectra with increased confidence is demonstrated, by combining results from successive tests with different Cited by: 6.
Results from impedance eduction methods developed by NASA Langley Research Center are used throughout the acoustic liner community. Occasional anomalies persist with these methods at Cited by: 6. Experimental validation of a two-dimensional shear-flow model for determining acoustic impedance [microf Pressure probe and hot-film probe responses to acoustic excitation in mean flow [microform] / Tony L.
Pa Evaluation of a multi-point method for determining acoustic impedance [microform] / Michael G. Jones and. Get this from a library. Evaluation of a multi-point method for determining acoustic impedance.
[Michael G Jones; Tony L Parrott; Langley Research Center.]. subsurface may not be prohibitive. Reflection seismic methods provide fine structural detail and refraction methods provide precise estimates of depth to lithologies of differing acoustic impedance.
The refraction method has been used in mineral investigations to map low-velocity alluvial deposits such as those that may contain gold, tin, or sand. quirements of the acoustic impedance matrix for calculation of the sound power using the boundary element method can be greatly reduced.
In order to compute the acoustic radiation modes, the impedance matrix needs to be symmetric. However, when using the boundary element method, it is often found that the impedance matrix is not symmetric. ThisCited by: 1. indirect method to evaluate the non-acoustic properties of a sound absorbing material by the use of a recently proposed three-microphone impedance tube method .
This three-microphone method was shown to be less heavy and more accurate than other existing methods to measure the effective acoustic by: The method is shown to converge to the normal incident impedance values and thus to be an adequate tool for determining the impedance of specimens in a grazing incidence, multi-modal.
The basic parameters of acoustic materials are the impedance and the sur-face shape. The equations given in Sect. are applicable as first-order approximations of the impedance and reflection factor of acoustic materi-als.
To discuss more details, other information such as angle-dependent impedance, porosity, tortuosity, etc., is Size: KB. Full text of "Comparison of Two Acoustic Waveguide Methods for Determining Liner Impedance" See other formats ^l _ _ _ _ / AIAA Comparison of Two Acoustic Waveguide IMetiiods for Determining Liner Impedance Michael G.
Jones, Willie R. Watson, Maureen B. Tracy, and Tony L. Parrott NASA Langley Research Center Hampton, VA 7tli AiAA/CEAS Aeroacoustics Conference May. Measurement of the strength of adhesive bonds in multi- layered structures is of increasing importance. Ultrasonic NDE methods do not directly determine the strength of a bond but indicate characteristics of a bond which may be related to bond strength through empirical relationships.
One such bond characteristic is its acoustic impedance. Impedance profiling methods have long been studied in Author: Nader Saffari, David T. Green. Acoustic methods (also known as sonic testing, vibration testing, mechanical impedance testing) depend on exciting vibrations in a specimen by a local impact and then measuring some properties of the vibrations, eg resonant frequency, decay time, etc.
Manfred Schroeder was a man with many interests. Between the years andhe invented devices for measuring the surface impedance of materials as well as the vocal tract impedance. At the Author: Roland Kruse, Volker Mellert. particle velocity. The term acoustic impedance (characteristic impedance) is defined by analogy with electrical systems as a p Z c v ==±ρ (5) Sound Intensity, Sound Power and Sound-Energy Density The sound intensity, I, is defined as the average rate of flow of sound energy (power)File Size: 1MB.
methods described in Section II can be used to determine the impedance of the test liner. For each data acquisition,averagesoneachmicrophonechannel(blocksofdatapointsperaverage)aretaken.
To reduce the inﬂuence of ﬂow noise, a cross-spectrum signal extraction method11 is File Size: 8MB. Devices and methods for calibrating acoustic cement evaluation data using an acoustic calibration device installed behind a casing in a wellbore are provided.
Such an acoustic calibration apparatus may be installed in contact with the outer diameter of a casing and cemented in place with cement in a wellbore. The acoustic calibration apparatus may include a first material different from that Cited by: 3.
Banks, G. Propst, and R. Silcox, Groups generated by wave-duct acoustics with impedance boundary conditions, CAMS Tech. Report #, University of Southern California, August,  M. Jones and T. Parrott, Evaluation of a multi-point method for determining acoustic impedance, Mechanical Systems and Signal Processing 3 Cited by: 4.
This test method is intended to provide a much faster measurement technique than that of Test Method C 5. Signiﬁcance and Use This test method can be applied to measure sound absorption coefficients of absorptive materials at normal inci-dence, that is, 0°.
It also can be used to determine speciﬁc impedance and admittance ratios. Ultrasonic is one of the most common uses of a non-destructive evaluation method for crack detection and characterization. The effectiveness of the acoustic-ultrasound Structural Health Monitoring (SHM) technique for the determination of the depth of the surface crack was by: The acoustic impedance (Z) of a material is defined as the product of its density (p) and acoustic velocity (V).
Z = pV. Acoustic impedance is important in. the determination of acoustic transmission and reflection at the boundary of two materials having different acoustic impedances.
the design of ultrasonic transducers. In order to obtain a high sensitivity, an impedance change of the GMI element caused by a magnetic field, has to yield a large change in the SAW reflected from the output IDT.
A model is presented to simulate the electro-acoustic interaction of the output IDT with the GMI sensor’s impedance and the impedance matching by: 5. acoustic impedance below the scan location. On the right side of Figure 1 the increased redundancy of information of MIRA (bottom) over conventional IE (top) can be observed, where the multi-static array of transmitting and receiving transducers creates 45 measurement angle pairs compared to one measurement pair in traditional IE.
Figure Size: 2MB. Now we will calculate the voltage VC by using the impedance method. In terms of the impedance the RLC circuit is ZR=R ZL=jL jC Vc +-ω ω 1 Zc= VS Figure 2 This is now a representation in the frequency domain since impedance is a frequency domain complex quantity The voltage VC may now be determined by applying the standard voltage divider File Size: KB.
using impedance tube. Various methods are available for measuring the acoustic properties of the materials. These methods include standing wave ratio method by Seybert A F and Ross D () , transfer function method Ideo et al., , two cavity method and two load method and reverberation method ASTM Ca .
The. It is an impedance which ranges between acoustic impedance (AI) and gradient impedance (GI). The method projects a line through the cloud of data points on a scatter plot, where AI and GI are displayed in the x- and y-axis, respectively.
Such AI/GI cross-plots is an effective way to discriminate different lithologies and fluid effects. Ultrasonic NDE methods do not directly determine the strength of a bond but indicate characteristics of a bond which may be related to bond strength through empirical relationships. One such bond characteristic is its acoustic impedance.
Impedance profiling methods have long been studied in the field of geophysics and medical ultrasonics [1,2].Author: Nader Saffari, David T.
Green. Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting from an acoustic pressure applied to the system.
The SI unit of acoustic impedance is the pascal second per cubic metre (Pas/m 3) or the rayl per square metre (rayl/m 2), while that of specific acoustic impedance is the pascal second per metre (Pas/m) or Characteristic: Symbols.
Topics Covered: Introduction to two port network - introduction to z or impedance parameters - Equational and matrix form of voltage equation - process of determining Z-parameters.
Start studying SPI # 4. Learn vocabulary, terms, and more with flashcards, games, and other study tools. In-situ measurement method of ensemble averaged impedance and absorption characteristics of materials at field incidence using p-v or p-p sensors Published at the InternoiseT.
Otsuru; An Iterative Method for Determining the Surface Impedance of Acoustic Materials In Situ Published at the InternoiseJ. Alvarez, F. Jacobsen.
Medical ultrasound (also known as diagnostic sonography or ultrasonography) is a diagnostic imaging technique, or therapeutic application of is used to create an image of internal body structures such as tendons, muscles, joints, blood vessels, and internal aim is often to find a source of a disease or to exclude practice of examining pregnant women using ICDCM: Here C 0 denotes the capacitance of the mechanically clamped transducer, Z C represents the acoustic impedance of the transducer with the area A, ω is the angular frequency, and β ¯ a is the effective wavenumber of longitudinal waves within the PZT transducer.
F 1,2 terms the normal forces at the transducer faces, T the associated normal stresses, v 1,2 the velocities (the indices 1 and 2 Cited by:. Sound waves propagate at different speeds through different materials generally moving faster through more dense materials.
The acoustic impedance (expressed as g/cm 2 μs) is the product of density (g/cm 3) and velocity (cm/μs).Of particular importance is the extreme difference between the impedance of air and that of any solid material.Ultrasonic Bond Log Physics (cont.)• Tools t 72 or readings per revolution• Wellbore fluid properties are measured – Fluid velocity (µs/in) – Fluid acoustic impedance in MRayl ( -1)• Fluid density, velocity and impedance parameters are required inputs to measure the impedance of the material behind the.The method is shown to reproduce the measured normal incidence impedance spectrum for each of the test liners, thus validating its usefulness for determining the normal incidence impedance of test liners for a broad range of source frequencies and flow Mach numbers.