Production of directionally limited acoustic power spectra

1991 ◽  
Vol 90 (2) ◽  
pp. 1213-1213
Author(s):  
Michael J. Greenwood ◽  
David P. J. Coughtrie
Keyword(s):  
Power Spectra ◽  
Acoustic Power

Analytical Acoustic Power Spectrum Formulations for Rotating Monopole and Dipole Point Sources

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yijun Mao ◽  
Chen Xu
Keyword(s):  
Power Spectrum ◽  
Power Spectra ◽  
Expansion Method ◽  
Acoustic Power ◽  
Point Sources ◽  
Harmonic Series ◽  
Dipole Source ◽  
Power Ratio ◽  
Good Agreement ◽  
Series Expansion Method

Analytical acoustic power spectrum formulations for the rotating monopole and dipole point sources are proposed by employing the spherical harmonic series expansion method. Both the analytical acoustic power spectra and the overall acoustic power show a good agreement with the results obtained from other methods. A nondimensional acoustic power ratio (APR) is employed to investigate the effects of the rotational Mach number, the direction of the dipole source, and the number of sources on the acoustic power output.

Spectral Properties and Quantitative Evaluation of Hypernasality in Vowels

1996 ◽  
Vol 33 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Ryuta Kataoka ◽  
Ken-Ichi Michi ◽  
Kaoru Okabe ◽  
Tanetoshi Miura ◽  
Hiroshi Yoshida
Keyword(s):  
Spectral Properties ◽  
Power Level ◽  
Power Spectra ◽  
Normal Subjects ◽  
Acoustic Power ◽  
Preliminary Study ◽  
A New Technique ◽  
Second Formant ◽  
The One ◽  
Nasal Resonance

A new technique for evaluating hypernasality using an acoustic approach is presented. In a preliminary study using this technique, nasal resonance was assessed in 17 normal subjects and 16 subjects judged to be hypernasal. Analyses of the one-third-octave power spectra revealed an increase in power level between the first and second formant, and a reduction in the power level in second and third formant regions among utterances judged to be hypernasal. Factor analysis of the perceptual ratings revealed that the consensus perception of hypernasality accounted for 71% of the total variance. An additional 8% was accounted for by individual differences. Multiple regression analysis revealed a high correlation between the consensus perception of hypernasality and the variance in two acoustic-power levels, these being the power level between the first and second formant and the power level of the second and third formant regions.

Structure- and Fluid-Borne Acoustic Power Sources in 90 Degree Piping Elbows Excited by Turbulent Flow

2006 ◽  
Author(s):  
Stephen A. Hambric ◽  
David A. Boger ◽  
John B. Fahnline ◽  
Robert L. Campbell
Keyword(s):  
Fluid Flow ◽  
Structural Parameters ◽  
Power Spectra ◽  
Acoustic Power ◽  
Flow Speed ◽  
Piping System ◽  
Power Sources ◽  
Turbulent Fluid Flow ◽  
Turbulent Fluid ◽  
Wall Pressure Fluctuations

The structure-borne and fluid-borne vibro-acoustic power spectra induced by turbulent fluid flow over the walls of a continuous 90 degree piping elbow are computed. Although the actual power input by the wall pressure fluctuations to the piping is distributed throughout the elbow, equivalent total powers input to various structural wavetypes (bending, torsion, axial) and fluid (plane waves) at the inlet and discharge of the elbow are computed. The powers at the elbow ‘ports’ are suitable inputs to wave-based and statistically-based models of larger piping systems that include the elbow. Calculations for several flow and structural parameters, including pipe wall thickness, flow speed, and flow Reynolds number are shown. The power spectra are scaled on flow and structural-acoustic parameters so that levels for conditions other than those considered in the paper may be estimated, subject to geometric similarity constraints (elbow radius/pipe diameter). The approach for computing the powers, which links Computational Fluid Dynamics, Finite Element and Boundary Element modeling, and efficient random analysis techniques, is general, and may be applied to other piping system components excited by turbulent fluid flow, such as U-bends and T-sections.

scholarly journals Distribution of Acoustic Power Spectra for an Isolated Helicopter Fuselage

2016 ◽  
Vol 114 ◽  
pp. 02062
Author(s):  
A.N. Kusyumov ◽  
S.A. Mikhailov ◽  
L.I. Garipova ◽  
A.S. Batrakov ◽  
G. Barakos
Keyword(s):  
Power Spectra ◽  
Acoustic Power

Towards a Universal Scaling for Broadband Turbulent Noise in Internal Flow Devices

2013 ◽  
Author(s):  
Arjen de Jong ◽  
Joachim Golliard
Keyword(s):  
High Speed ◽  
Scaling Laws ◽  
Scaling Law ◽  
Power Spectra ◽  
Internal Flow ◽  
Acoustic Power ◽  
Broadband Noise ◽  
Current Work ◽  
Sound Power ◽  
Noise Sources

An investigation is performed on the scalability of broadband noise sources from separated flows in internal pipe systems. Broadband sources from for example wellhead chokes, bends and valves can potentially excite subsea manifolds through fluid acoustic coupling and fluid structural coupling. The focus of the current work is evaluation and improvement of scaling laws for collapse of sound power spectra. The approach proposed here is to use steady-state Computational Fluid Dynamics [CFD] to better estimate the properties of the flow in order to improve the scaling law and obtain a universal broadband spectrum. Steady Reynolds Averaged Navier-Stokes [RANS] simulations of several bend and orifice geometries have been performed. A surface acoustic power model based on modeled turbulent quantities is implemented. Based on the RANS data, more advanced models for scaling have been developed. Experimental sound power spectra from literature of the simulated geometries are scaled using different methodologies in both amplitude and frequency. When a new scaling based on CFD modeled surface acoustic power was used, a universal collapse among geometries occurred. Using CFD, the velocity in the high-speed sound-producing region is obtained, as well as a more accurate length scaling in order to improve the frequency scaling. A vast improvement in collapse over different geometries is achieved. The current work indicates that a universal collapse might indeed be present. The methodology does not require high fidelity calculations and is thus easy to implement. By comparing original and new scaling laws, it turns out that the ratio of fluctuating drag over steady drag can vary among geometries.

Image formation analysis of thick biological specimens using three-dimensional power-spectra of through focus series

1994 ◽  
Vol 52 ◽  
pp. 124-125
Author(s):  
Karen F. Han
Keyword(s):  
Inelastic Scattering ◽  
Imaging Techniques ◽  
Mass Density ◽  
Relative Proportion ◽  
Three Dimensional ◽  
Power Spectra ◽  
Image Formation ◽  
Energy Filtering ◽  
Ewald Sphere ◽  
Nonlinear Imaging

The primary focus in our laboratory is the study of higher order chromatin structure using three dimensional electron microscope tomography. Three dimensional tomography involves the deconstruction of an object by combining multiple projection views of the object at different tilt angles, image intensities are not always accurate representations of the projected object mass density, due to the effects of electron-specimen interactions and microscope lens aberrations. Therefore, an understanding of the mechanism of image formation is important for interpreting the images. The image formation for thick biological specimens has been analyzed by using both energy filtering and Ewald sphere constructions. Surprisingly, there is a significant amount of coherent transfer for our thick specimens. The relative amount of coherent transfer is correlated with the relative proportion of elastically scattered electrons using electron energy loss spectoscopy and imaging techniques.Electron-specimen interactions include single and multiple, elastic and inelastic scattering. Multiple and inelastic scattering events give rise to nonlinear imaging effects which complicates the interpretation of collected images.

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