Vibration-induced Noise Research Articles

Noise Evaluation for Pavement Maintenance in Metropolitan Highway Bridges

Dynamic response of a bridge under traffic load induces acoustic energy at the bridge surface. The acoustic energy change generates an additional coupled noise component caused by vibration of a bridge deck associated with the pavement conditions and moving velocity of the vehicle. This paper presents a three-dimensional finite-element method developed for the dynamic response and noise propagation model, and analyzes the coupled effect induced by traffic loading based on different pavement conditions. Even though vibration-induced noise at the bridge is below the audible frequency range of 20–20,000 Hz , it amplifies the traffic noise source to the highly annoyed level of noise in the metropolitan area. Among several factors that contribute to the traffic noise, interaction between pavement and vehicle is considered according to the different surface roughness and vehicle velocity. The result shows that poor pavement condition contributes to the increase of traffic noise at a high traveling speed of the ...

Nonlinear dynamics of planetary gears using analytical and finite element models

Vibration-induced gear noise and dynamic loads remain key concerns in many transmission applications that use planetary gears. Tooth separations at large vibrations introduce nonlinearity in geared systems. The present work examines the complex, nonlinear dynamic behavior of spur planetary gears using two models: (i) a lumped-parameter model, and (ii) a finite element model. The two-dimensional (2D) lumped-parameter model represents the gears as lumped inertias, the gear meshes as nonlinear springs with tooth contact loss and periodically varying stiffness due to changing tooth contact conditions, and the supports as linear springs. The 2D finite element model is developed from a unique finite element-contact analysis solver specialized for gear dynamics. Mesh stiffness variation excitation, corner contact, and gear tooth contact loss are all intrinsically considered in the finite element analysis. The dynamics of planetary gears show a rich spectrum of nonlinear phenomena. Nonlinear jumps, chaotic motions, and period-doubling bifurcations occur when the mesh frequency or any of its higher harmonics are near a natural frequency of the system. Responses from the dynamic analysis using analytical and finite element models are successfully compared qualitatively and quantitatively. These comparisons validate the effectiveness of the lumped-parameter model to simulate the dynamics of planetary gears. Mesh phasing rules to suppress rotational and translational vibrations in planetary gears are valid even when nonlinearity from tooth contact loss occurs. These mesh phasing rules, however, are not valid in the chaotic and period-doubling regions.

Measurement-while-drilling surveying of highly inclined and horizontal well sections utilizing single-axis gyro sensing system

In the oil industry, when developing a plan for drilling horizontal wells, measurement-while-drilling (MWD) surveying becomes one of the important prerequisites for the successful completion of the drilling process. MWD surveying of horizontal wells determines the position and the orientation of the bottom hole assembly (BHA) in real-time during the drilling operation. The BHA orientation is determined by its inclination from the vertical direction as well as its azimuth. The present MWD surveying system incorporates three-axis accelerometers and three-axis magnetometers mounted in three mutually orthogonal directions. This magnetic surveying system suffers from the deviation of the magnetic field measurements due to the massive amount of steel around the drilling rig. A new method utilizing the fibre optic gyroscopes (FOG) technology was suggested to replace the magnetic surveying system. It was reported that a single FOG mounted inside the bearing assembly with its sensitive axis along the tool spin axis could be incorporated with three-axis accelerometers to continuously survey the near-vertical well section. This study aims at suggesting a surveying methodology for highly inclined and horizontal well sections utilizing FOG sensors. At each surveying station, the intrinsic uncertainties of the surveying sensors and the other vibration-induced noise are reduced using a transversal finite impulse response filter. The inclination is then computed by processing the accelerometer measurements, while the gyro measurement is utilized to determine the azimuth. In addition, optimal estimation techniques based on Kalman filtering are used to improve the azimuth accuracy and to limit the effect of the drift of the surveying sensors over time. This study indicates that gyroscopic surveying utilizing the FOG technology can be a reliable solution for MWD surveying of horizontal wells.

Noise in microelectromechanical system resonators

Microelectromechanical system (MEMS) and nanoelectromechanical system (NEMS) based resonators and filters, ranging in frequencies from kHz to GHz, have been proposed. The question of how the stabilities of such resonators scale with dimensions is examined in this paper, with emphasis on the noise characteristics. When the dimensions of a resonator become small, instabilities that are negligible in macro-scale devices become prominent. The effects of fluctuations in temperature, adsorbing/desorbing molecules, outgassing, Brownian motion, Johnson noise, drive power and self-heating, and random vibration are explored. When the device is small, the effects of fluctuations in the numbers of photons, phonons, electrons and adsorbed molecules can all affect the noise characteristics. For all but the random vibration-induced noise, reducing the dimensions increases the noise. At submicron dimensions, especially, the frequency noise due to temperature fluctuations, Johnson noise, and adsorption/desorption are likely to limit the applications of ultra-small resonators.

Vibration compensation technique for an optical current transducer

Details are presented on a technique for compensation of vibration-induced noise in an optical current transducer (OCT). The light intensity changes that result from vibration are reciprocal, i.e., their magnitude does not depend on the direction of light propagation. However, intensity changes that result from the Faraday rotation induced as the light travels through the OCT are dependent on the direction of propagation and hence, by using two counter-propagating beams, vibration- induced intensity noise can be canceled by applying simple signal processing. This solution also enables true dc current measurement to be made. The principles of operation of the compensation method an experimental evaluation of the system are presented and the limitations associated with the compensation scheme are discussed.

Active vibration reduction in a light weight high speed train bogie

Active control of vibration-induced noise in light weight train cars is of great interest since low weight trains are more economic but also have higher internal noise levels. This paper describes an approach to isolate bogie vibrations in such a way that the noise inside the car is reduced. An active control system with four inertial mass actuators fitted to the bogie were used to control bogie vibrations and noise inside the car. The tests were performed on an experimental light weight bogie fitted to a test car, in both lab environment and in foil scale tests on track at full speed.

Properties of PCLT/P(VDF-TrFE) 0–3 nanocomposites

Calcium and lanthanum modified lead titanate (PCLT) powder with size in the nanometer range was prepared using a sol-gel technique. PCLT powder annealed at 850°C was incorporated into a polyvinylidene fluoride/trifluoroethylene P(VDF-TrFE) copolymer matrix to form 0.15 mm thick films of 0–3 nanocomposites with ceramic volume fraction (φ) ranging from 0.05 to 0.33. The dielectric and pyroelectric properties of the composites were measured as functions of temperature. The observed permittivity and dielectric loss were found to agree with the predictions of the Bruggeman model. When the ceramic and copolymer phases in these nanocomposites are poled in the same direction, the pyroelectric activities of the two phases reinforce while the piezoelectric activities partially cancel, thereby minimizing the vibration-induced electrical noise in pyroelectric current measurements.

PCLT/P(VDF-TrFE) 0–3 nanocomposite thin films for pyroelectric applications

Nanocrystalline calcium and lanthanum modified lead titanate (PCLT) powder was prepared by a solgel process followed by annealing at 850°C. 0–3 nanocomposite thin films of PCLT powder dispersed in a vinylidene fluoride /trifluoroethylene (P(VDF-TrFE)) copolymer matrix were fabricated on glass substrates using the spin-coating technique. The permittivity, pyroelectric coefficient, specific heat and pyroelectric figures-of-mer-it were measured as functions of the volume fraction (φ) of ceramic for φ up to 0.16. Single-element pyroelectric sensors with PCLT/P(VDF-TrFE) nanocomposites as the sensing elements were fabricated and characterized. The voltage and current responsivities Rv and Ri of the sensors were measured as functions of frequency and found to agree well with the calculated values. Since the pyroelectric coefficients of PCLT and P(VDF-TrFE) have like signs while the piezoelectric coefficients have opposite signs, the poled composite has high pyroelectric but low piezoelectric activity, thereby reducing the vibration-induced electrical noise in pyroelectric sensor applications.

Nanocrystalline Lead Titanate and Lead Titanate/Vinylidene Fluoride‐Trifluoroethylene 0‐3 Nanocomposites

Lead titanate (PT) powders of nanometer particle sizes were prepared using a sol‐gel process. The PT gel was annealed at various temperatures to produce powders with different particle sizes. X‐ray diffractometry (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) revealed that the PT gel initially crystallized at an annealing temperature of 500°C. The crystallite diameter measured by XRD increased from 27 to 54 nm, while the size of PT particles increased from 30 to 270 nm as the annealing temperature increased from 500° to 900°C. Lead titanate/vinylidene fluoride‐trifluoroethylene (PT/P(VDF‐TrFE)) 0‐3 nanocomposites with PT volume fractions of 0.18 and 0.41 were prepared using PT powders annealed at various temperatures. Because the pyroelectric coefficients of the ceramic and polymer phases had like signs and the piezoelectric coefficients had opposite signs, the poled composite had high pyroelectric but very low piezoelectric activity, thereby reducing vibration‐induced electrical noise in pyroelectric sensor applications.

Novel hybrid interferometer stabilization scheme used in wavelength shift measurement for Bragg grating sensors

A novel hybrid interferometer stabilization scheme used for wavelength shift measurement, such as for in-fiber Bragg grating-based sensors, is described. This scheme combines the advantages of the long term optical imbalance stability offered by the locking system used and a comparative insensitivity to vibration-induced noise at frequencies up to 200 Hz, achieved with the use of a so-called “detection-and-compensation” scheme. By including an additional reference beam and the hybrid interferometer stabilization scheme, the vibration-induced fluctuation in the signal can be reduced by about 20 dB, and the value of the phase variation can be reduced by a factor of 20.

Analysis of the effect of vibration-induced noise in different fibre leads used in an optical current-measurement system

The noise induced by environmental perturbations, such as vibration in fibre leads, degrades the performance of an optical current-measurement system, and should be suppressed. Vibration-induced noise in three types of fibre leads, single-mode, highly birefringent, and multimode fibre, has been measured when used in such an optical current-measurement system, and the effect quantified and discussed. The results have shown that vibration-induced noise may be suppressed in highly birefringent fibre by choosing carefully the input angle of a linearly polarized beam or by using a low-coherence source in the sensor. The noise observed can be effectively eliminated by employing a long length of multimode fibre and a low-coherence source, combined with appropriate coupling conditions.

Frequency Jitter from Mechanical Vibrations in a Diode Laser Mounted on a Closed-Cycle Refrigerator

Frequency jitter in a tunable diode laser output due to impact shocks produced by the closed-cycle refrigerator has been characterized as a function of the piston movement during different phases of the cycle. An analysis of the influence of the vibration-induced noise suggests a random (Gaussian) contribution to the laser spectrometer lineshape.

The linearization of vibration-induced noise

The problem of linearizing the neutron noise induced by a vibrating absorber is discussed fully. First it is shown by a formal proof why the traditional linearization method of noise theory, based solely on the smallness of the vibration amplitude, is not applicable. Then a linearization technique, correct to the first order of the vibration amplitude, is introduced and the case of strong-absorber vibrations is solved correctly. The results are interpreted and compared with those given by the weak-absorber approximation, whereby a close functional similarity is found. Finally, applicability of the latter is examined numerically and deviation from the exact results is found to be small in realistic situations.