The Modal Formulation and Adaptive-Passive Control of the Nonself-Adjoint One-Dimensional Acoustic System With a Mass-Spring Termination

1999 ◽  
Vol 66 (1) ◽  
pp. 242-249
Author(s):  
V. Jayachandran ◽  
J. Q. Sun
Keyword(s):  
Passive Control ◽  
Noise Control ◽  
Numerical Study ◽  
Adjoint Operator ◽  
Forced Response ◽  
Interior Noise ◽  
Single Frequency ◽  
Acoustic System ◽  
One Dimensional ◽  
Mass Spring

This paper investigates the use of mass-spring type of impedances as absorbing elements for interior noise control. The general modal formulation for a one-dimensional acoustic system terminated by a spring-supported piston is presented. The boundary value problem has a nonself-adjoint operator which renders the mode functions unorthogonal. This is overcome by defining an associated self-adjoint operator in Hilbert space and using an operator-theoretic formulation of the problem. Orthogonal mode functions and an expansion theorem are presented which can be used to construct a series solution for the forced response. A numerical study is performed for the case of single frequency excitation in which the impedance parameters are optimized by minimizing the cost function. The results from the numerical simulations indicate the feasibility of interior noise control using tunable mechanical impedances, and provide guidelines and restrictions in designing such a system.

Vibration Absorbers: A Review of Applications in Interior Noise Control of Propeller Aircraft

2004 ◽  
Vol 10 (8) ◽  
pp. 1221-1237 ◽  
Author(s):  
R. I. Wright ◽  
M. R. F. Kidner
Keyword(s):  
Passive Control ◽  
Noise Control ◽  
Large Body ◽  
Research Area ◽  
Interior Noise ◽  
Vibration Absorbers ◽  
Noise Levels ◽  
Active Systems ◽  
Significant Research ◽  
Fruitful Research

Control of interior noise levels in aircraft has been a significant research area over the last two decades. Vibration absorbers have often been researched as more efficacious solutions to this problem than absorbent blankets or fully active systems. In this paper we review the large body of work performed in this field and we offer an indication of the remaining areas for fruitful research. Surprisingly few installations of vibration absorbers for interior noise control have been realized, and we believe this is due to the pervasive belief in industry that vibration absorbers can only be applied to control resonant, not forced behavior in a structure. The potential of adaptive passive control using vibration absorbers has been shown by many researchers, and we believe that this direction may yield several practical solutions to the problem of interior noise in aircraft.

scholarly journals Phononic metastructures with ultrawide low frequency three-dimensional bandgaps as broadband low frequency filter

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad ◽  
C. W. Lim
Keyword(s):  
Passive Control ◽  
Noise Control ◽  
Three Dimensional ◽  
Low Frequency ◽  
Resonant Mode ◽  
Frequency Range ◽  
Research Activities ◽  
Vibration Attenuation ◽  
Mass Spring ◽  
Broadband Frequency

AbstractVibration and noise control are among the classical engineering problems that still draw extensive research interest today. Multiple active and passive control techniques to resolve these problems have been reported, however, the challenges remain substantial. The recent surge of research activities on acoustic metamaterials for vibration and noise control are testimony to the fact that acoustic metamaterial is no longer limited to pure theoretical concepts. For vibration and noise control over an ultrawide frequency region, 3-D metastructures emerge as a novel solution tool to resolve this problem. In that context, the present study reports a novel proposal for 3-D monolithic phononic metastructures with the capability to induce low frequency ultrawide three-dimensional bandgaps with relative bandwidth enhancements of 157.6% and 160.1%. The proposed monolithic metastructure designs consist of elastic frame assembly that is connected with the rigid cylindrical masses. Such structural configuration mimics monoatomic mass-spring chain where an elastic spring is connected with a rigid mass. We develop an analytical model based on monoatomic mass-spring chain to determine the acoustic mode frequency responsible for opening the bandgap. The wave dispersion study reveals the presence of ultrawide bandgaps for both types of metastructures. The modal analysis shows distribution of vibration energy in the bandgap opening (global resonant mode) and closing (local resonant mode) bounding edges. We further analyze the band structures and discuss the physical concepts that govern such ultrawide bandgap. Vibration attenuation inside the bandgap frequency range is demonstrated by frequency response studies conducted by two different finite element models. Thanks to additive manufacturing technology, 3-D prototypes are prepared and low amplitude vibration test is performed to validate the numerical findings. Experimental results show the presence of an ultrawide vibration attenuation zone that spreads over a broadband frequency spectrum. The bandgaps reported by the proposed metastructures are scale and material independent. The research methodology, modelling and design strategy presented here may pave the way for the development of novel meta-devices to control vibration and noises over a broadband frequency range.

One-dimensional numerical study of compressible flow ejector

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 1469-1472
Author(s):  
S. Han ◽  
J. Peddieson
Keyword(s):  
Compressible Flow ◽  
Numerical Study ◽  
One Dimensional

Active control for vehicle interior noise using the improved iterative variable step-size and variable tap-length LMS algorithms

2019 ◽  
Vol 67 (6) ◽  
pp. 405-414 ◽  
Author(s):  
Ningning Liu ◽  
Yuedong Sun ◽  
Yansong Wang ◽  
Hui Guo ◽  
Bin Gao ◽  
...  
Keyword(s):  
Steady State ◽  
Noise Control ◽  
Convergence Speed ◽  
Interior Noise ◽  
Lms Algorithm ◽  
Variable Step Size ◽  
Step Size ◽  
Vehicle Interior ◽  
Vehicle Interior Noise ◽  
Variable Step

Active noise control (ANC) is used to reduce undesirable noise, particularly at low frequencies. There are many algorithms based on the least mean square (LMS) algorithm, such as the filtered-x LMS (FxLMS) algorithm, which have been widely used for ANC systems. However, the LMS algorithm cannot balance convergence speed and steady-state error due to the fixed step size and tap length. Accordingly, in this article, two improved LMS algorithms, namely, the iterative variable step-size LMS (IVS-LMS) and the variable tap-length LMS (VT-LMS), are proposed for active vehicle interior noise control. The interior noises of a sample vehicle are measured and thereby their frequency characteristics. Results show that the sound energy of noise is concentrated within a low-frequency range below 1000 Hz. The classical LMS, IVS-LMS and VT-LMS algorithms are applied to the measured noise signals. Results further suggest that the IVS-LMS and VT-LMS algorithms can better improve algorithmic performance for convergence speed and steady-state error compared with the classical LMS. The proposed algorithms could potentially be incorporated into other LMS-based algorithms (like the FxLMS) used in ANC systems for improving the ride comfort of a vehicle.

scholarly journals Numerical Modeling of the Interaction of Solitary Waves and Submerged Breakwaters with Sharp Vertical Edges Using One-Dimensional Beji & Nadaoka Extended Boussinesq Equations

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Mohammad H. Jabbari ◽  
Parviz Ghadimi ◽  
Ali Masoudi ◽  
Mohammad R. Baradaran
Keyword(s):  
Solitary Waves ◽  
Numerical Study ◽  
Time Integration ◽  
Boussinesq Equations ◽  
Linear Interpolation ◽  
Reflected Waves ◽  
One Dimensional ◽  
Propagating Waves ◽  
Linear Elements ◽  
Predictor Corrector

Using one-dimensional Beji & Nadaoka extended Boussinesq equation, a numerical study of solitary waves over submerged breakwaters has been conducted. Two different obstacles of rectangular as well as circular geometries over the seabed inside a channel have been considered in view of solitary waves passing by. Since these bars possess sharp vertical edges, they cannot directly be modeled by Boussinesq equations. Thus, sharply sloped lines over a short span have replaced the vertical sides, and the interactions of waves including reflection, transmission, and dispersion over the seabed with circular and rectangular shapes during the propagation have been investigated. In this numerical simulation, finite element scheme has been used for spatial discretization. Linear elements along with linear interpolation functions have been utilized for velocity components and the water surface elevation. For time integration, a fourth-order Adams-Bashforth-Moulton predictor-corrector method has been applied. Results indicate that neglecting the vertical edges and ignoring the vortex shedding would have minimal effect on the propagating waves and reflected waves with weak nonlinearity.

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