Search results for "Transmission loss"
showing 8 items of 8 documents
Application of alternating projection method to ensure feasibility of shadowing cross-correlation models
2007
A novel procedure based on the alternating projection method to adjust experimental shadowing cross-correlation (SCC) matrices is proposed. Given an SCC matrix derived from any experimental model, this procedure finds the nearest diagonalisable correlation matrix. This adjustment allows a proper simulation of shadowing samples, since it produces correlation matrices for which Cholesky factorisation is feasible. Simulation results using this procedure for three different SCC models are compared and discussed.
Efficient Low-Frequency Modal Analysis of Anechoic Chamber
2007
An efficient method to analyze the electromagnetic field inside rectangular anechoic and semianechoic chambers from 30 to 100 MHz is shown. A modal expansion is employed to develop the homogeneous and the inhomogeneous field. This is combined with circuital techniques to compute the effect of the layers of ferrite and dielectrics in the walls of the chamber. Several numerical results of the Free Space Transmission Loss (FSTL) of an anechoic chamber and the Normalized Site Attenuation (NSA) of a semianechoic chamber are provided.
Design and Study of a Wide-Band Printed Circuit Board Near-Field Probe
2021
Magnetic near-field probes (NFP) represent a suitable tool to measure the magnetic field level from a small electromagnetic interference (EMI) source. This kind of antenna is useful as a magnetic field probe for pre-compliance EMC measurements or debugging tasks since the user can scan a printed circuit board (PCB) looking for locations with strong magnetic fields. When a strong H-field point is found, the designer should check the PCB layout and components placement in that area to detect if this could result in an EMI source. This contribution focuses on analyzing the performance of an easy to build and low-cost H-field NFP designed and manufactured using a standard PCB stack-up. Thereby,…
An optimal dimensioning method of a green wall structure for noise pollution reduction
2021
International audience; This paper concern the optimization of a multilayered green wall structure including substrate and foliage in order to reduce as much as possible backward noise reflection and forward transmission from the wall. Each component involved in the wall structure is fully characterized experimentally to get its transfer matrix. Simulation demonstrated that foliage layer superimposed to substrate layer doesn’t affect the transmission losses but contributes greatly to the increase of return losses of the green wall structure. To achieve the best performances in terms of return and forward losses as well as frequency bandwidth, the methods of optimization are discussed inclu…
New Acoustic Test Chambers at the University of Palermo
2008
Acoustic test chambers at the University of Palermo have been completed after a design optimization of existent building structures. A unique building houses five reverberation chambers, differently coupled each other in order to achieve a large flexibility on testing procedures, and offices for the staff. Main measurements offered to national and international standards include determination of sound power, sound insulation and sound absorption. Reverberation chambers present peculiar geometries in order to achieve the desidered sound fields. Chambers structure and layout within the whole building, housing all the acoustic facilities, has been designed in order to achieve strong sound insu…
Characterization of impervious layers using scale models and an inverse method
2009
We describe a novel procedure that uses an inverse method to determine unknown parameters for impervious layers used in multilayer structures. The proposed model of the multilayer structure is limited to an ideal double plate separated by an unbonded, fibrous, sound-absorbing material. Experimental data were obtained by nearfield acoustic holography for the calculation of the transmission loss of various multilayer structures mounted in a window in a wooden box designed specifically for this purpose. We used the Trochidis and Kalaroutis forecast model of acoustic insulation for multilayer structures, which is based on a spatial Fourier transform. The experimental pressure and velocity data …
Sedimentation and Fouling of Optical Surfaces at the ANTARES Site
2003
ANTARES is a project leading towards the construction and deployment of a neutrino telescope in the deep Mediterranean Sea. The telescope will use an array of photomultiplier tubes to detect the Cherenkov light emitted by muons resulting from the interaction with matter of high energy neutrinos. In the vicinity of the deployment site the ANTARES collaboration has performed a series of in-situ measurements to study the change in light transmission through glass surfaces during immersions of several months. The average loss of light transmission is estimated to be only ~2% at the equator of a glass sphere one year after deployment. It decreases with increasing zenith angle, and tends to satur…
Acoustical properties of air-saturated porous material with periodically distributed dead-end pores
2015
International audience; A theoretical and numerical study of the sound propagation in air-saturated porous media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at " nodes " periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscous and thermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical pro…