Experimental study for control of sound transmission through double glazed window using optimally tuned Helmholtz resonators

This paper presents an experimental investigation of passively control of sound transmission through a double glazed window by using arrangement of Helmholtz resonators (HRs), which are commonly used for narrow band control application. The laboratory experiments were performed placing the window between reverberation chamber and anechoic chamber. The window was subject to diffuse field, approximate normal wave and oblique wave acoustic excitations. Three sets of HRs were designed and installed in cavity of window. The sound control performances at far-field were measured. The control performances from varying the number of HRs, incident acoustic field, excitation sources (band-limited white noise and traffic noise examples) are presented and discussed in detail. It is shown that a considerable reduction of the transmitted sound pressure levels has been achieved around the mass–air–mass resonance frequency (50–120 Hz). The obtained reductions in the transmitted sound pressure illustrate the potentials of HRs for improving the sound insulation characteristics of double glazed window. The experimental results also indicate that only tuning the HRs to the mass–air–mass resonance frequency does not guarantee the best possible insulation of the sound transmission.     

Numerical modeling of sound propagation in an inhomogeneous waveguide with absorption

Computation of the acoustic field in vertically and horizontally inhomogeneous waveguides with allowance for absorption is considered. The method of normal waves and the parabolic equation method are used as alternative approaches to the problem. The efficiency of the algorithms suggested is demonstrated by a test example of sound propagation in a wedge with the acoustic velocity depending on the depth.State University, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 1–2, pp. 134–138, January–February, 1995.     

Sound field of normal modes in a stratified medium with a plane-parallel stream

Expressions for the sound field and radiated power of a pointwise harmonic source in a stratified medium with a plane-parallel stream are presented and discussed.Institute for Physics of Microstructures, Russian Academy of Sciences, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 1–2, pp. 122–126, January–February, 1995.     

Temperature anomalies in the dispersion and absorption of sound near phase transition points at low temperatures

We examined the attenuation and dispersion of sound during phase transitions with an overdamped soft mode at low temperatures. The obtained temperature and frequency dependences differ from results known at the high-temperature asymptote. The temperature anomalies are sharper. At low frequencies, the attenuation behaves like (T – T_c)^–5/2 for a critical phonon spectrum isotropic in k, and like (T–T_c)^–2 for uniaxial ferroelectrics. The presence of a temperature anomaly is characteristic also for high-frequency attenuation, behaving like (T–T_c)^–1/2 and ln(T–T_c)., respectively. We discuss briefly the results obtained from an experimental test.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 70–74, January, 1989.     

Prediction of flow-generated noise produced by acoustic and aerodynamic interactions of multiple in-duct elements

Flow-generated noise problem caused by in-duct elements is due to the complicated acoustic and turbulent interactions of multiple in-duct flow noise sources. The approach of partially coherent sound fields used previously by Mak and Yang [C.M. Mak, J. Yang, Flow-generated noise radiated by the interaction of two strip spoilers in a low speed flow ducts, Acta Acust united with Acustica 88 (2002) 861–868] and Mak [C.M. Mak, A prediction method for aerodynamic sound produced by multiple elements in air ducts, J Sound Vib 287 (2005) 395–403] is adopted to formulate the sound powers produced by interactions of multiple elements at frequencies below and above the cut-on frequency of the lowest transverse duct mode. The study indicates that the level and spectral distribution of the additional acoustic energy produced by the interactions of multiple elements can be predicted based on the measured data with respect to the interactions. The proposed method can form a basis of a generalized prediction method for flow-generated noise produced by multiple elements. The application of the proposed method is supported by two engineering examples.     

Radio-wave backscattering from artificial ionospheric turbulence

Conclusions The feasibility of investigating the inhomogeneous structure of the perturbed region obtained with the use of a high-power ionospheric station located at a small distance from the heater station is demonstrated. It is shown that the test wave signals backscattered by the perturbed region in the 5–10 MHz frequency range have appreciable amplitudes. The use of several frequencies of test waves and computations of the trajectories for determining the position of the scattering volume permits investigation of the perturbed region in a large height range. The experiments showed that the region occupied by the artificial inhomogeneities extends to more than 50 km below the level of reflection of the heater wave. The characteristic dimensions of the scattering inhomogeneities are estimated (l ~ 40–90 m,l ~ 2–2.5 km.).Scientific-Research Institute of Radiophysics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 28, No. 5, pp. 579–584, May, 1985.     

Schallgeschwindigkeitsmessungen in Schmelzen aus den Systemen Al−Mg,Al−Sn,Mg−Sn und Fe−C

The concentration dependency of sound velocity was measured in molten alloys of the three systems Al–Mg, Al–Sn, and Mg–Sn in the temperature region between liquidus and 1000°C. Furthermore it was measured in molten alloys of the system Fe–C in the temperature range between liquidus temperatureT _L andT _L+150°C. From the velocities the compressibilities were calculated, whose concentration dependency revealed changes in the structure of the melts.The structure of the three systems Al–Mg, Al–Sn, and Mg–Sn in the molten state was already investigated by X-Ray diffraction. These results were compared with the results of velocity measurements. Inhomogeneities in the melts yield increased values of compressibility compared with the values to be expected for statistical distribution of the atoms. This result was used for the discussion of the structure of molten Fe-C-alloys:The conclusion can be drawn, that within the melts of the system Fe–C above 3^w/0 C inhomogeneities are existent.From the values of sound velocity in the molten elements the temperature dependency of the structure factorsI(0) was calculated and compared with experimental values.

---

---

Teil der Dissertation von U. Maier, Universität Stuttgart, 1972.     

Efficient computation of compressible and incompressible flows

The combination of explicit Runge–Kutta time integration with the solution of an implicit system of equations, which in earlier work demonstrated increased efficiency in computing compressible flow on highly stretched meshes, is extended toward conditions where the free stream Mach number approaches zero. Expressing the inviscid flux Jacobians in terms of Mach number, an artificial speed of sound as in low Mach number preconditioning is introduced into the Jacobians, leading to a consistent formulation of the implicit and explicit parts of the discrete equations. Besides extension to low Mach number flows, the augmented Runge–Kutta/Implicit method allowed the admissible Courant–Friedrichs–Lewy number to be increased from O(1 0 0) to O(1 0 0 0). The implicit step introduced into the Runge–Kutta framework acts as a preconditioner which now addresses both, the stiffness in the discrete equations associated with highly stretched meshes, and the stiffness in the analytical equations associated with the disparity in the eigenvalues of the inviscid flux Jacobians. Integrated into a multigrid algorithm, the method is applied to efficiently compute different cases of inviscid flow around airfoils at various Mach numbers, and viscous turbulent airfoil flow with varying Mach and Reynolds number. Compared to well tuned conventional methods, computation times are reduced by half an order of magnitude.     

Effect of deep dislocation levels in silicon on the properties of p-n junctions

We present the results of studies on the influence of deep levels, due to dislocations in electronic-grade silicon, on the lifetime of minority carriers and on the current-voltage and capacitance-voltage characteristics of p-n junctions. The parameters of the deep levels were determined by means of dynamic spectroscopy. The carrier lifetime in the high-resistance region of the p-n junction correlates well with the dislocation density and varies from 10^–7 sec to 3 · 10^–8 sec when the dislocation density N_d varies from 10⁷ cm^–2 to 5 · 10³ cm^–2. The voltage across the p-n junction at a high level of injection varies 1.6 to 6.2 v as a function of N_d. The ionization energy of deep levels associated with dislocation in silicon is 0.44 and 0.57 eV, measured from the bottom of the conduction band.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 81–84, January, 1988.     

Active suppression of radiating wavenumbers in the dynamic response of submerged plates

The sound radiated from an electrically excited piezoelectric plate is computed. Voltage distributions obtainable from an array of finite sized electrodes are used to examine the possibility of actively suppressing sound radiated at particular spatial wavenumbers. An application to canceling the reflection of a plane wave at oblique incidence is presented. The results presented here can also be found in Barbone & Braga (1992).Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 8, pp. 848–852, August, 1993.     

Synthesis of βGa2O3 nanowires by an MOCVD approach

We have synthesized monoclinic gallium oxide (βGa₂O₃) nanowires on Au-coated Si substrates by a reaction of a trimethylgallium and oxygen mixture. The βGa₂O₃ nanowires became progressively thinner from bottom to top, with diameters ranging from 10 to 200 nm and lengths of several micrometers. We found that Au-containing nanoparticles were attached to the tips of the βGa₂O₃ nanowires and thus the nanowire growth could be a vapor–liquid–solid process .PACS 81.07.-b; 81.15.Gh     

Combination of time reversal and synthetic aperture beamforming for active detection of small bottom objects in waveguide environments

To enhance detection of small targets, the combination of time reversal processing (TRP) and synthetic aperture beamforming (SABF) is investigated. With the spatial–temporal focusing, the potential application of TRP for active detection has been demonstrated [Kim S, Kuperman WA, Hodgkiss WS. Echo-to reverberation enhancement using a time reversal mirror. J Acoust Soc Am 2004;115(4):1525–31]. When a physical probe source (PS) replaced by a modeled source (MS), the “potential” is turned into being more practical. Similar to matched field processing, the robustness of TRP with MS needs to be considered. Meanwhile by the improvement of the extended towed array measurement (ETAM) algorithm of passive SABF, a segmented ETAM algorithm is discussed for its use in active sonar. With the echo-signal enhancement by time reversal transmission, the echo-to-reverberation ratio is further improved by SABF. Finally a matched filter is used to detect the target and the range of the target is estimated by the time delay referenced to the transmission time. The results of the waveguide tank experiment demonstrate that the TRP–SABF method can effectively detect and locate a bottom cylinder shell of 0.51 m long and 0.21 m in diameter.     

Local levels in a zinc sulfide film

The energies and densities of the local levels in an epitaxial ZnS film grown on a GaAs substrate are determined by methods based on thermally-stimulated currents, thermal deexcitation, and the photoluminescence spectrum. Levels are found at depths of 0.17, 0.2, 0.25, 0.31–0.33, 0.41, and 0.71 eV from the bottom of the conduction band and 1.15 eV from the top of the valence band. These results are compared with published data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 95–98, October, 1973.     

Dielectric constant and current transport for HfO2 thin films on ITO

The dielectric constant and leakage current mechanisms for HfO₂ thin films deposited on indium–tin–oxide using reactive rf sputtering deposition were examined. Indium–tin–oxide was selected as the bottom metal as it is of interest as an electrode in transparent field-effect transistor development. The dielectric constant of HfO₂ films was approximately 20 and did not vary significantly with deposition conditions. Temperature-dependent leakage current measurements indicate that Schottky emission is the dominant transport mechanism in films deposited at low temperature and/or low oxygen pressure. The HfO₂/indium–tin–oxide barrier height was extracted to be 1.1±0.2 eV. Films deposited at high temperature and/or oxygen pressure deviate from the Schottky emission model, presumably due to the formation of polycrystalline material with grain boundary conduction. PACS  73.61.Ng; 73.50.Lw; 77.55.+f     

Secondary radiation of the semiconducting solid solution Zn x Cd1−x S during selective excitation

We present the results of spectroscopic studies of secondary radiation of the solid solution Zn_xCd_1–xS (0.05相似文献   

Attenuation of sound by inhomogeneities in the transition parameter and critical fluctuations near phase transitions

The temperature singularities in the critical fluctuations and the sound attenuation resulting from a nonzero inhomogeneous distribution of the transition parameter have been investigated. This effect is related to a rearrangement of the crystal lattice near an impurity center. It is shown that the corresponding contributions to the kinetic coefficients which have been studied are comparable to the correlation corrections but have a different dependence on the quantity (T – T_c), where T is the absolute temperature and T_c is the Curie temperature.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 60–65, October, 1978.     

Dispersion law and lifetime of holes with negative effective masses in Γ1v band of crystals having the diamond structure

It is shown that in the bottom valence band _1v of crystals, having the diamond structure, holes are described by a standard dispersion law with a negative effective mass. Interaction of these holes with phonons is considered. The lifetime of holes due to this interaction is estimated. In Ge, at 20°K, it can reach 10^–9 sec.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 10–13, February, 1984.     

Wave losses during friction

Wave losses during friction caused by independent movable vibration (sound) sources are calculated on the basis of concepts of the relation between the Poynting vector and external frictional force.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 73–78, May, 1972.     

Experimental results of the performance of a laser fiber as a remote sensor of temperature

We present experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor. The sensor is based on the fluorescence intensity-ratio change of two spectral bands as a function of temperature in the wavelength interval from 515 to 570 nm. We apply a radiometric analysis to the fluorescence spectrum that we have measured to determine the optimal spectral bands to use in the power ratio of the sensor. The spectral bands used in the power ratio, with best performance, are 525–535 nm/555–565 nm, with a signal–noise ratio of 57 and 56 dB, respectively. The sensor sensitivity is about , and the resolution is approximately .     

Time-dependent electromagnetic perturbations in a magnetized plasma with relaxing conductivity

The problem of one-dimensional propagation of a time-dependent electromagnetic perturbation in a homogeneous ionospheric plasma with relaxing conductivity in the presence of a horizontal geomagnetic field is considered. The approximate Green's function is constructed assuming that the dynamics of electromagnetic perturbations is determined by the diffusion mechanism if the diffusion is due to the sound wave motion. It is found that the relaxation of plasma conductivity may result in a solitary perturbation precursor preceding the arrival of the sound wave front.State University, St. Petersburg. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 668–677, July, 1995.