Frequency response smoothing, matrix assembly and structural paths: A new approach for structural dynamics up to high frequencies

1990 ◽  
Vol 137 (1) ◽  
pp. 53-68 ◽  
Author(s):  
A. Girard ◽  
H. Defosse
Keyword(s):  
Frequency Response ◽  
Structural Dynamics ◽  
Matrix Assembly ◽  
New Approach ◽  
High Frequencies

scholarly journals Diffuse-Field Equalisation of Binaural Ambisonic Rendering

2018 ◽  
Vol 8 (10) ◽  
pp. 1956 ◽  
Author(s):  
Thomas McKenzie ◽  
Damian Murphy ◽  
Gavin Kearney
Keyword(s):  
Virtual Reality ◽  
Frequency Response ◽  
Sound Source ◽  
High Frequency ◽  
Sagittal Plane ◽  
Impulse Responses ◽  
Spectral Difference ◽  
High Frequencies ◽  
Listening Tests ◽  
Frequency Reproduction

Ambisonics has enjoyed a recent resurgence in popularity due to virtual reality applications. Low order Ambisonic reproduction is inherently inaccurate at high frequencies, which causes poor timbre and height localisation. Diffuse-Field Equalisation (DFE), the theory of removing direction-independent frequency response, is applied to binaural (over headphones) Ambisonic rendering to address high-frequency reproduction. DFE of Ambisonics is evaluated by comparing binaural Ambisonic rendering to direct convolution via head-related impulse responses (HRIRs) in three ways: spectral difference, predicted sagittal plane localisation and perceptual listening tests on timbre. Results show DFE successfully improves frequency reproduction of binaural Ambisonic rendering for the majority of sound source locations, as well as the limitations of the technique, and set the basis for further research in the field.

scholarly journals Model Updating Method Based on Kriging Model for Structural Dynamics

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Hong Yin ◽  
Jingjing Ma ◽  
Kangli Dong ◽  
Zhenrui Peng ◽  
Pan Cui ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Frequency Response ◽  
Structural Dynamics ◽  
Model Updating ◽  
Computational Cost ◽  
Element Model ◽  
Kriging Model ◽  
Surface Model ◽  
Sample Points

Model updating in structural dynamics has attracted much attention in recent decades. And high computational cost is frequently encountered during model updating. Surrogate model has attracted considerable attention for saving computational cost in finite element model updating (FEMU). In this study, a model updating method using frequency response function (FRF) based on Kriging model is proposed. The optimal excitation point is selected by using modal participation criterion. Initial sample points are chosen via design of experiment (DOE), and Kriging model is built using the corresponding acceleration frequency response functions. Then, Kriging model is improved via new sample points using mean square error (MSE) criterion and is used to replace the finite element model to participate in optimization. Cuckoo algorithm is used to obtain the updating parameters, where the objective function with the minimum frequency response deviation is constructed. And the proposed method is applied to a plane truss model FEMU, and the results are compared with those by the second-order response surface model (RSM) and the radial basis function model (RBF). The analysis results showed that the proposed method has good accuracy and high computational efficiency; errors of updating parameters are less than 0.2%; damage identification is with high precision. After updating, the curves of real and imaginary parts of acceleration FRF are in good agreement with the real ones.

Externally Pressurized Bearings—II: Vibration Attenuators

1968 ◽  
Vol 90 (3) ◽  
pp. 614-617 ◽  
Author(s):  
D. F. Wilcock ◽  
W. E BeVier
Keyword(s):  
Frequency Response ◽  
Closed Loop ◽  
Magnetic Hysteresis ◽  
Rolling Element Bearings ◽  
High Frequencies ◽  
Gear Teeth ◽  
Hydrostatic Bearing ◽  
Performance Factors ◽  
Rolling Element ◽  
Turbine Blading

Rolling element bearings are vibration generators, and in addition are stiff, so that they transmit rotor generated noise as well to the machine frame and casing. Self-acting (hydrodynamic) bearings are also very rigid, so that they are excellent transmitters of rotor generated vibration, e.g., front gear teeth, turbine blading, or magnetic hysteresis. A typical rotor weighing 1000 lb may be supported on bearings having a stiffness of 3 × 106 lb/in., and hence will be a good vibration transmitter up to a frequency of 172 cps. Hydrostatic bearings afford an opportunity to control the bearing frequency response so that attenuation of middle and high frequencies can be secured. Analysis of the hydrostatic bearing as a closed-loop servomechanism reveals methods of designing them for attenuation without serious consequences in other performance factors. They may be used as the primary bearing, or as separate isolator bearings in conjunction with rolling element or self-acting bearings. Some examples of possible applications are discussed.

Measurement of the Dynamic Model of a PUMA 560 Robot Using Experimental Modal Analysis

1994 ◽  
Vol 116 (1) ◽  
pp. 75-79 ◽  
Author(s):  
P. Elosegui
Keyword(s):  
Frequency Response ◽  
Structural Dynamics ◽  
Measurement Technique ◽  
Mode Shape ◽  
Linear Models ◽  
Response Model ◽  
Response Functions ◽  
Model Accuracy ◽  
Nonlinear Characteristics ◽  
Modal Model

This paper presents two different models of the structural dynamics of a PUMA 560 robot: a frequency response, and a modal model. The first consists of a set of frequency response functions measured from the structure. The eigenvalues and the mode-shape, which comprise the modal model, are extracted from the response model. In addition to these linear models, the paper describes the nonlinear characteristics of the structure. How the non-linearities affect the measurement technique and the model accuracy is also described.

Multiobjective Pareto-Based Optimization of pMUT Hydrophone With Piezoelectric Active Diaphragm

2014 ◽  
Author(s):  
Sergey Shevtsov ◽  
Shun-Hsyung (Stephen) Chang ◽  
Valery Kalinchuk ◽  
Igor Zhilyaev ◽  
Maria Shevtsova
Keyword(s):  
Frequency Response ◽  
Vacuum Chamber ◽  
Ultrasonic Transducers ◽  
Fe Model ◽  
Spatial Averaging ◽  
New Approach ◽  
Ultrasound Field ◽  
Sound Detection ◽  
Membrane Type ◽  
Micro Electromechanical System

The design of high-sensitive hydrophones is one of the research interests in underwater acoustics. Due to progress of micro- and nanotechnology the most attention of researchers is attracted by the transducers that use the micro-electromechanical system (MEMS) concept. Piezoelectric micro-machined ultrasonic transducers (pMUTs) present a new approach to sound detection and generation that can overcome the shortcomings of conventional transducers. For accurate ultrasound field measurement, small size hydrophones which are smaller than the acoustic wavelength are required for providing an omnidirectional response and avoid spatial averaging. This paper presents some results of multiobjective optimization for membrane-type piezoceramic MEMS based transducers. We investigate the miniaturized membrane-type sensor with perforated holes in the active PZT and intermediate membranes, with the protective plates and a vacuum chamber. An influence of the protective plate elastic and viscous properties, the dimensions and the relative area of the perforated holes on the sensitivity’s frequency response of the hydrophone was studied for the broadening and equalizes the operating frequency band. We optimize these key parameters using the Pareto approach with the finite element (FE) model of coupled piezoelectric-acoustic problem. Finally, the set of optimized hydrophone structures and some examples of obtained sensitivity frequency response are demonstrated.

Interaural Intensity and Time Differences in Anechoic and Reverberant Rooms

1967 ◽  
Vol 10 (2) ◽  
pp. 177-185 ◽  
Author(s):  
Donald Dirks ◽  
John P. Moncur
Keyword(s):  
Frequency Response ◽  
Sound Pressure ◽  
Anechoic Chamber ◽  
Intensity Level ◽  
Average Response ◽  
Response Curves ◽  
Interaural Time Differences ◽  
High Frequencies ◽  
Intensity Changes ◽  
Free Environment

The purpose of this investigation was to describe the physical characteristics of an artificial head and to determine the interaural time and intensity changes which occurred at selected azimuths. Measurements were conducted in a reflection free environment and in controlled reverberation conditions. The frequency response of the head microphones simulated the average response curves at the human auditory canal. In the anechoic chamber, the sound pressure at the ear nearest the speaker remained constant as the head moved from 0° azimuth to 45° and 90°. A reduction in intensity was observed in the far ear at azimuths of 45° and 90°. The decrease in sound pressure was observed in the middle and high frequencies. A “build-up” in the intensity level was found during the reverberant conditions. In the anechoic chamber, interaural time differences ranged from 0.42 to 0.56 msec at 45° azimuth and from 0.76 to 0.81 msec at 90° azimuth.

Reducing Tire-Induced Noise and Vibration2

2006 ◽  
Vol 34 (2) ◽  
pp. 135-147
Author(s):  
C. Yilmaz ◽  
G. M. Hulbert ◽  
N. Kikuchi
Keyword(s):  
Frequency Response ◽  
Cost Effective ◽  
Vehicle Speed ◽  
New Approach ◽  
Noise And Vibration ◽  
Suspension Systems ◽  
Daunting Task ◽  
Wide Range ◽  
Practical Performance ◽  
New Perspective

Abstract Tire-induced noise and vibration spans a wide range of frequencies, depending on, among other attributes, tread design, road surface, and vehicle speed. Vehicle designers are faced with the daunting task of minimizing this broad frequency of energy. The design of suspension systems must take into account the need to have a well-tuned frequency response. In this paper, a new approach toward minimizing tire-induced noise and vibration is presented. The methodology is based upon a new perspective of employing antiresonance, as opposed to damping phenomena, to effectively tune systems for practical performance. The mechanical structure of the system is amenable to cost-effective manufacture and can be packaged in different configurations. We present the fundamental approach toward the design and give several example configurations.

Estimation of Frequency Response Function on Rotational Degrees of Freedom of Structures

1999 ◽  
Author(s):  
Naoki Hosoya ◽  
Takuya Yoshimura
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Structural Dynamics ◽  
Frequency Response Function ◽  
Degrees Of Freedom ◽  
Estimation Procedure ◽  
Rigid Block ◽  
Measurement Point ◽  
Beam Structure ◽  
Rotational Degrees Of Freedom

Abstract In conventional vibration testing, measurement of frequency response function (FRF) has been limited to translational degrees of freedom (DOF). Rotational DOFs have not been treated in experimental analysis. However, the rotational DOF is indispensable in further analysis, such as substructure synthesis, prediction of structural dynamics modification, etc. Hence, measurement of FRFs on rotational DOF is essential for expanding applicability of experimental modal analysis. This paper proposes a new method for FRF estimation on rotational DOF of structures. The following is the estimation procedure: A rigid block is fixed on the measurement point of the structure; the block is excited by conventional impact hammer; the inner force and the response of the connection point including rotational DOFs are estimated; and lastly, the FRF including rotational DOF at the connection point of the structure is obtained. The feasibility of the method is investigated experimentally by applying it to a beam structure.

Sign in / Sign up

Export Citation Format

Share Document