Search results for "NOISE"
showing 10 items of 1375 documents
Alteraciones del sueño producidas por el ruido ambiental*
1989
ResumenEste articulo presenta los resultados de una encuesta realizada con el objetivo de valorar distintos aspectos relacionados con el ruido ambiental y sus efectos sobre determinadas comunidades urbanas. Un total de 263 residentes en 5 emplazamientos diferentes de la ciudad de Valencia fueron entrevistados. En estos 5 emplazamientos se realizaron de manera independiente una serie de medidas de los niveles de ruido durante las 24 horas del dia y en distintos días de la semana.:El 400%0 de los encuestados manifestó tener alguna dificultad para dormirse y el 59% de ellos lo atribuyó al ruido causado por el tráfico. Asimismo, un 49% de los encuestados declaró despertarse durante la noche (el…
The Community Response to Aircraft Noise Around Six Spanish Airports
1993
Abstract The community response to aircraft noise has been studied through a social survey. A total of 1800 persons living in the vicinity of six major Spanish airports have been interviewed at their homes concerning the environmental quality of the area, dissatisfaction with road traffic noise and aircraft noise, activities interfered with by noise, most disturbing aircraft types, and subjective evaluation of airport impact. All the responses obtained in this survey have been compared with aircraft noise levels corresponding to the residence locations of the people interviewed (values of NEF levels were calculated with the INM model). The results obtained in this work allow one to evaluate…
A PROCEDURE FOR THE EVALUATION OF INSTALLED PROPELLER NOISE
2001
Abstract A method for the prediction of the acoustics of a propeller in the flow-field of a wing is presented. The method is used to study the noise generated by the unsteady loading induced on the propeller as it passes through the wing flow-field. Both the aerodynamic and acoustic methods are previously proven techniques, the aerodynamic method being based on a combination of free wake analysis and a three-dimensional boundary element method, while the acoustic calculation is a full-surface, moving medium form of the Ffowcs Williams–Hawkings equation. Calculations are presented for a reference case of a four-bladed low-speed propeller in forward flight. The acoustic predictions are supple…
A study of noise transmission through cylindrical shell using modal truncation approach
2011
International audience; The study of the vibroacoustic behaviour of cylindrical structure like aircraft fuselage requires the establishment of very large models, and the numerical results which can be obtained are often difficult to interpret. On the other hand, the study of simple structures such as cylindrical shells is useful to validate the criteria and tools that can be used to simplify the models of complex structures. The presented study concerns the sound transmission through a cylindrical shell coupled to a cavity and subjected to an incident acoustic wave. Noise reduction is obtained and validated by a numerical method which uses structural and acoustical modes. A criterion for se…
Viscoelastic bearings with fractional constitutive law for fractional tuned mass dampers
2015
Abstract The paper aims at studying the effects of the inherent fractional constitutive law of viscoelastic bearings used as devices for tuned mass dampers. First, the proper constitutive law of the viscoelastic supports is determined by the local constitutive law. Then, the characteristic force–displacement relationship at the top of the bearing is found. Taking advantage of the whole bearing constitutive laws, the tuning of the mass damper is proposed by defining the damped fractional frequency, which is analogous to the classical damped frequency. The effectiveness of the optimal tuning procedure is validated by a numerical application on a system subjected to a Gaussian white noise.
Speed and rotor flux estimation of induction motors via on-line adjusted extended kalman filter
2006
This paper deals with the estimation of speed and rotor flux of induction motors via Extended Kalman Filter (EKF) with on-line adjusting of the system noise covariance matrix. The predictor of EKF consists of a discrete time model obtained by means of a second order discretization of the original nonlinear model of the induction motor. In order to obtain accurate estimation of the above mentioned variables, the load torque is included in the state variables and then estimated. Three different system noise models are also illustrated and compared each other by simulations carried out in Matlab/Simulink environment. For one of these models, EKF is adjusted on-line by means of an additional PI…
Quasi-digital conversion for resistive devices: application in GMR-based IC current sensors
2013
Resistive devices, including sensors, are used in a huge range of applications within different scenarios. When a complete system is considered, a quasi-digital output is often recommendable. If the conversion is operated at device level, some problems such as noise disturbs, insertion losses and so on, can be reduced. In this work, we describe a resistance-tofrequency (R-f) converter with a suggested application in low current monitoring by means of GiantMagnetoResistance (GMR) sensors. Specific devices have been designed and microfabricated. The system has been tested by means of discrete components with a PCB. The complete microsystem monolithic integration in a standard CMOS technology …
Uncertainty evaluation in the measurements for the electric power quality analysis
2013
The paper deals with the uncertainty estimation in the measurements performed to assess the electric power quality. In a first steps, according to the 'ISO - Guide to Expression of the Uncertainty in Measurements' all the error sources, which give a significant contribution to the combined uncertainty associated to the measurement results, are identified. Successively, in order to analyze how the errors propagate through the measurement chain, a Monte Carlo based approach is proposed. The method exploits an ad-hoc developed simulator of the measurement process, which takes into account the particular way of propagation of all the identified error sources. Eventually, with the aim of validat…
Robust control of stochastic systems against bounded disturbances with application to flight control
2014
This paper investigates the problems of state observer design and observer-based integral sliding-mode control (SMC) for a class of Itô stochastic systems subject to simultaneous input and output disturbances. A new type of sliding-mode-based descriptor observer method is developed to approximate the system state and disturbance vectors. An integral-type SMC scheme is proposed based on the state estimation to stabilize the overall system. The main contributions of this approach are as follows: 1) The desired estimations of state and disturbance vectors can be obtained simultaneously, and 2) in the designed sliding-mode observer, the integral term of the Itô stochastic noise is eliminated …
Characterization of electromagnetic noise suppression sheet for aerospace applications
2016
Electromagnetic noise suppression sheets based on absorber materials can be an interesting solution to reduce or suppress noise emissions at a high-frequency region that may cause complex EMI problems. These materials usually are characterized by their permeability but their performance also depend on other factors such as dimension, geometry, thickness or noise source kind. Three experimental methods are proposed in order to characterize absorber sheets in different kind of applications taking into account the last factors. These setups make it possible to test several samples with different characteristics and to analyse the absorption capacity in applications with transmission line probl…