The Experts below are selected from a list of 50484 Experts worldwide ranked by ideXlab platform
Linda P. Franzoni - One of the best experts on this subject based on the ideXlab platform.
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A high‐frequency broadband energy‐intensity boundary element method for specular reflection in three‐dimensional reverberant enclosures
The Journal of the Acoustical Society of America, 2006Co-Authors: Jerry W. Rouse, Linda P. Franzoni, Donald B. BlissAbstract:A new method is presented for predicting the spatial variation of mean‐Square Pressure within three‐dimensional enclosures having steady‐state, high‐frequency broadband sound fields. The enclosure boundaries are replaced by a continuous distribution of uncorrelated broadband directional sources, which provide constituent fields expressed in terms of mean‐Square Pressure and time‐averaged intensity variables. Boundary conditions for radiating and absorbing surfaces are recast in energy and intensity variables. Superposition of these source fields in a numerical boundary element formulation leads to the prediction of overall mean‐Square Pressure and time‐averaged intensity as a function of position. Both specular and diffuse reflection boundaries can be accommodated. In contrast to the traditional boundary element approach, this method is independent of frequency, and each element has multiple unknowns, namely the strengths of directivity harmonics. For verification, exact analytical solutions for the mean‐...
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Absorption‐based scaling method to predict steady‐state broadband sound fields in enclosures
The Journal of the Acoustical Society of America, 2006Co-Authors: Donald B. Bliss, Jerry W. Rouse, Linda P. FranzoniAbstract:An absorption‐based analysis method is developed for steady‐state broadband sound fields in enclosures having diffuse or specular reflection boundaries. The wall absorption is expressed as an overall spatially averaged value, with spatial variations around this mean. Interior Pressures and intensities are expressed in a power series of the overall absorption, treated as a small parameter, thereby giving a separate problem at each order. The first problem has a uniform mean‐Square Pressure level proportional to the reciprocal of the absorption parameter, as expected. The second problem gives a mean‐Square Pressure and intensity distribution that is independent of the absorption parameter and is primarily responsible for the spatial variation of the reverberant field. This problem depends on the location of sources and the spatial distribution of absorption, but not absorption level. Higher‐order problems proceed at powers of the absorption parameter, but are essentially small corrections to the primary spa...
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Prediction of broadband nonuniform time‐dependent acoustic fields in enclosures with diffuse reflection boundaries using energy‐intensity modes
The Journal of the Acoustical Society of America, 2004Co-Authors: Donald B. Bliss, Linda P. FranzoniAbstract:A new analysis of high‐frequency broadband reverberant sound fields in rooms with diffuse reflection boundaries is described. Depending on shape, source location, and distribution of wall absorption, rooms exhibit spatial variation in steady‐state mean‐Square Pressure and also spatial dependence of decay time characteristics. The room boundaries can be replaced by a distribution of uncorrelated broadband directional energy‐intensity sources. In steady state with diffuse reflection boundaries, the interior Pressure field produced by these sources satisfies Laplace’s equation. The mean‐Square Pressure field is expressed as a sum of constituent modes. The intensity field, which is related to the Pressure field in a complex way, can be calculated for each mode. Boundary conditions relate averaged intensity and Pressure. The mean‐Square Pressure is expressed in terms of the modal sum. Lower order modes are responsible for the overall smooth spatial variation in the reverberant field; higher modes account for m...
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A broadband energy‐based boundary element method for predicting vehicle interior noise
The Journal of the Acoustical Society of America, 2004Co-Authors: Linda P. Franzoni, Jerry W. Rouse, Tracy A. DuvallAbstract:Efficient calculation of vehicle interior noise is a challenging task. Classical acoustic boundary element calculations become costly at high frequencies due to the very large number of elements required and must be solved repeatedly for broadband applications. An alternative energy‐intensity boundary element method has been formally developed that employs uncorrelated broadband directional intensity sources to predict mean‐Square Pressure distributions in enclosures. The boundary source directivity accounts for local correlation effects and specular reflection. The method is applicable to high modal density fields, but it is not restricted to the usual low‐absorption, diffuse, and quasi‐uniform assumptions. The approach can accommodate fully specular reflection, or any combination of diffuse and specular reflection. This new method differs from the classical version in that the element size is large compared to an acoustic wavelength and equations are not solved on a frequency‐by‐frequency basis. These differences lead to an orders‐of‐magnitude improvement in computational efficiency. In vehicle interiors the sources are typically the vibrating walls of the enclosure. A special treatment for wall vibration sources has been developed for use with the new boundary element method. Calculations of spatially varying mean‐Square Pressures agree well with computationally intensive modal solutions.
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An experimental and theoretical investigation of the high frequency broadband soundfield
The Journal of the Acoustical Society of America, 2002Co-Authors: Linda P. FranzoniAbstract:A relatively simple theoretical model of a rectangular enclosure with sound sources on one wall, an absorptive end‐wall, and two absorptive side‐walls is developed. Using a power balance at cross sections, a differential equation for mean‐Square Pressure in the acoustic enclosure is derived. A simple formula for the mean‐Square Pressure as a function of distance from source‐wall to absorbing end‐wall is obtained. The other variables in the formula include the random incidence absorption coefficients, the cross‐sectional area and perimeter, and the source power. This formula is compared to results from numerical simulations, to a revised Sabine prediction for mean‐Square level, and to experimental results. For the most absorptive cases, however, a more refined theoretical model is needed in order to have reasonable agreement with the experimental data. In the refined model, it is assumed sources are distributed on an end‐wall and the resulting sound waves are considered on an angle‐by‐angle basis. The mean‐Square Pressure is calculated by integrating over all possible angles. Although still a fairly simple result, the effects of angle of incidence on the absorption and the reflection field in the enclosure are retained.
H. Chang - One of the best experts on this subject based on the ideXlab platform.
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Hydraulic Square Pressure generator for dynamic calibration of Pressure sensors at low frequencies
Sixth International Symposium on Precision Engineering Measurements and Instrumentation, 2010Co-Authors: H. Chang, Tsing-tshih Tsung, Ching-song Jwo, S. H. WangAbstract:A hydraulic Square Pressure generator with a unique spool valve has been developed for use in a system to calibrate and evaluate the dynamic characteristics of Pressure sensors. This hydraulic Square Pressure generator generates a hydraulic Square Pressure with a rapid transient response in the time domain and with abundant harmonics in the frequency domain at low fundamental frequencies, rather than Square Pressure with poor harmonics at high fundamental frequencies. Its rise time and fundamental frequency are around 32.0 μs and 5 Hz, respectively, supporting a wide range of dynamic calibration of hydraulic Square Pressure generators. The sensing cavity in the hydraulic Square Pressure generator constrains the Pressure transient produced by the fluid in the valve and maintains the generated hydraulic Square Pressure for both tested and reference Pressure sensors. Three Pressure sensors are calibrated using the hydraulic Square Pressure produced by the system with an auto-regressive exogenous model. Their transfer functions are obtained by applying the common pole-zero principle to describe their dynamic characteristics in the frequency domain.
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Dynamic Performance of Flow Control Valve Using Different Models of System Identification
Key Engineering Materials, 2010Co-Authors: H. ChangAbstract:This study measures the dynamic characteristics of flow control valve by a self-developed Square Pressure wave generator (SPWG). Comprised of a revolving shaft and a fixed ring, SPWG generates Square Pressure waves by the differential function of rotation between these two critical components. With the highly sensitive piezoelectric Pressure sensor as the reference sensor, tests are conducted concurrently using a flow control valve. Under the same experimental parameters, the dynamic characteristics of flow control valve are evaluated by four kinds of system identification methods, namely ARX (Auto-Regressive with eXogenous input model), ARMAX (Auto-Regressive moving Average with eXogenous input model), OE (Output Error model) and BJ (Box-Jenkins model). The experimental results indicate that the dynamic performance of the tested flow control valve for resonance frequency, resonance peak and damping ratio are 1565.6 Hz, 0.9753 db and 0.4044, respectively.
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Analysis of the dynamic characteristics of Pressure sensors using ARX system identification
Sensors and Actuators A: Physical, 2008Co-Authors: H. Chang, Po Kai TzenogAbstract:Abstract While most analyses on hydraulic systems focus mainly on their static characteristics, a good understanding of their dynamic characteristics is of equal importance. Using a self-developed Square Pressure wave generator (SPWG), this study explores the dynamic characteristics of Pressure sensors in hydraulic systems using system identification analysis. As a replacement of the traditional directional control valve, the developed SPWG can achieve high-frequency switching by the differential effect between the revolving shaft and fixed ring. The Square Pressure waves generated serve as inputs into the hydraulic system. With the high-sensitivity piezoelectric Pressure sensor as the reference sensor, tests are conducted concurrently using a strain gauge Pressure sensor, a piezoelectric Pressure sensor and a piezoresistive Pressure sensor. The output signals obtained from the Pressure sensors are analyzed using the auto-regressive exogenous (ARX) system identification and the common pole–zero principle to reveal important dynamic characteristics including frequency response, transfer function, resonant frequency and damping ratio of the Pressure sensors.
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Study of Frequency Response of Control Components in a Pneumatic System
Journal of Testing and Evaluation, 2004Co-Authors: Tsing-tshih Tsung, H. Chang, Liangchia Chen, Wu Jia-lin, Lee-long HanAbstract:The study explores the frequency response characteristics of the control components in a pneumatic system, while developing a set of the most effective measurement methods and equipment that provides the closest dynamic characteristics of the pneumatic system. First, the study inputs Square Pressure wave signals, which have various frequencies and are generated by directional control valves, into the pneumatic system, which is comprised of an electromagnetic valve, pneumatic pipes, and Pressure sensors. In addition, the study discusses the influences of the aforementioned electromagnetic valve, pneumatic pipes, and Pressure sensors on the frequency responses of the pneumatic system through the analyses of outputted Pressure signals. Next, the study replaces the electromagnetic valve with the Square Pressure wave generator developed in the study that emits Pressure Square waves with frequencies up to 500 Hz to be inputted into premeasured Pressure sensors in the pneumatic system for testing the dynamic characteristics of the Pressure sensors at high frequencies. The study proposes applying Square Pressure waves to the dynamic property analyses of pneumatic components, i.e., inputs Square Pressure waves into premeasured Pressure sensors through the excitement method to the Pressure sensor and utilizes spectrum analysis for analyzing the outputted voltage signals. The experimental results can be provided for designers of pneumatic systems as references for selecting components and rectifying the system properties.
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analysis of dynamic characteristics of Pressure sensors using Square Pressure wave theory and system identification
Measurement Science and Technology, 2003Co-Authors: Tsing-tshih Tsung, H. Chang, Liangchia Chen, Jia Lin WuAbstract:Most analyses on Pressure sensors focus mainly on their static characteristics, while their dynamic characteristics have rarely been explored. In the field of applied engineering, a Pressure sensor with a quick response rate and high stability is required to reflect the dynamic behaviour of the hydraulic system. This study developed a Square Pressure wave generator to replace the traditional directional control valve. The developed generator can generate a Square Pressure wave of as high as 2 kHz and can achieve high-frequency switching by utilizing the differential principle through a series of mechanical rotations between the revolving spindle and revolving ring. The Square Pressure wave generated is input into the hydraulic system while the output voltage signals given by the Pressure sensor can be analysed by spectrum analysis and system identification to obtain various dynamic characteristics of the Pressure sensor, including transfer function, natural resonance frequency and damping ratio.
Massimo Iovino - One of the best experts on this subject based on the ideXlab platform.
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testing steady state analysis of single ring and Square Pressure infiltrometer data
Geoderma, 2016Co-Authors: Vincenzo Bagarello, Massimo IovinoAbstract:Testing reliability of the saturated soil hydraulic conductivity, K-s, estimated by applying the steady-state single-ring (SR) model to the quasi steady-state infiltration rates obtained with a single-ring Pressure infiltrometer (PI) increases confidence in the estimated K-s values. Determining a means to estimate K-s from infiltration data collected with a Square infiltrometer allows the use of sources of different shapes. Using numerically simulated infiltration rates for six homogeneous soils ranging in texture from sand to silty clay loam, this investigation suggested an overall good performance of the SR model, with estimated K-s values differing by not more than 25% from the true values for the 90% of the 96 considered runs. Larger errors were generally obtained for the silty clay loam soil. Even in this case, however, a small ring radius (0.038 m), a relatively high initial soil water content (initial effective saturation = 0.4) and a relatively high depth of ponding (0.10 m) allowed the obtainment of accurate predictions of K-s (error = 13%) with a run of practically sustainable duration (4 h). The SR model was also usable to analyze quasi steady-state infiltration data collected with a Square infiltrometer when infiltration was assumed to occur through a circular source having the same area of the Square infiltrometer. With this assumption, the estimates of K-s differed from the true values by not more than a practically negligible 16%. The results of this investigation should help better interpret K-s values obtained with the PI and also improve the experimental methodology, depending on the soil. Moreover, a wider applicability of the infiltrometer techniques, i.e. not limited to a circular source, can be expected. Soil heterogeneity should be taken into account in the future since heterogeneity is common in the field. (C) 2015 Elsevier B.V. All rights reserved.
Dara M. Farrell - One of the best experts on this subject based on the ideXlab platform.
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the underwater sound field from vibratory pile driving
Journal of the Acoustical Society of America, 2015Co-Authors: Peter H. Dahl, David R Dallosto, Dara M. FarrellAbstract:Underwater noise from vibratory pile driving was observed using a vertical line array placed at range 16 m from the pile source (water depth 7.5 m), and using single hydrophones at range 417 m on one transect, and range 207 and 436 m on another transect running approximately parallel to a sloping shoreline. The dominant spectral features of the underwater noise are related to the frequency of the vibratory pile driving hammer (typically 15–35 Hz), producing spectral lines at intervals of this frequency. The mean-Square Pressure versus depth is subsequently studied in third-octave bands. Depth and frequency variations of this quantity observed at the vertical line array are well modeled by a field consisting of an incoherent sum of sources distributed over the water column. Adiabatic mode theory is used to propagate this field to greater ranges and model the observations made along the two depth-varying transects. The effect of shear in the seabed, although small, is also included. Bathymetric refraction o...
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The underwater sound field from vibratory pile driving.
The Journal of the Acoustical Society of America, 2015Co-Authors: Peter H. Dahl, David R. Dall'osto, Dara M. FarrellAbstract:Underwater noise from vibratory pile driving was observed using a vertical line array placed at range 16 m from the pile source (water depth 7.5 m), and using single hydrophones at range 417 m on one transect, and range 207 and 436 m on another transect running approximately parallel to a sloping shoreline. The dominant spectral features of the underwater noise are related to the frequency of the vibratory pile driving hammer (typically 15-35 Hz), producing spectral lines at intervals of this frequency. The mean-Square Pressure versus depth is subsequently studied in third-octave bands. Depth and frequency variations of this quantity observed at the vertical line array are well modeled by a field consisting of an incoherent sum of sources distributed over the water column. Adiabatic mode theory is used to propagate this field to greater ranges and model the observations made along the two depth-varying transects. The effect of shear in the seabed, although small, is also included. Bathymetric refraction on the transect parallel to the shoreline reduced mean-Square Pressure levels at the 436-m measurement site.
Po Kai Tzenog - One of the best experts on this subject based on the ideXlab platform.
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Analysis of the dynamic characteristics of Pressure sensors using ARX system identification
Sensors and Actuators A: Physical, 2008Co-Authors: H. Chang, Po Kai TzenogAbstract:Abstract While most analyses on hydraulic systems focus mainly on their static characteristics, a good understanding of their dynamic characteristics is of equal importance. Using a self-developed Square Pressure wave generator (SPWG), this study explores the dynamic characteristics of Pressure sensors in hydraulic systems using system identification analysis. As a replacement of the traditional directional control valve, the developed SPWG can achieve high-frequency switching by the differential effect between the revolving shaft and fixed ring. The Square Pressure waves generated serve as inputs into the hydraulic system. With the high-sensitivity piezoelectric Pressure sensor as the reference sensor, tests are conducted concurrently using a strain gauge Pressure sensor, a piezoelectric Pressure sensor and a piezoresistive Pressure sensor. The output signals obtained from the Pressure sensors are analyzed using the auto-regressive exogenous (ARX) system identification and the common pole–zero principle to reveal important dynamic characteristics including frequency response, transfer function, resonant frequency and damping ratio of the Pressure sensors.
