Improvement in the Acoustic Characteristics of the Micro Speaker by Changing Thickness and Foaming Ratio of the Diaphragm

2013 ◽  
Vol 718-720 ◽  
pp. 1310-1315
Author(s):  
Takeshi Nomoto ◽  
Takeru Moriuchi ◽  
Toru Fujii
Keyword(s):  
Fem Analysis ◽  
Cellular Phone ◽  
Frequency Characteristics ◽  
Experimental Result ◽  
Frequency Range ◽  
Acoustic Characteristics ◽  
Aluminum Sheets ◽  
Magnet Coil ◽  
Natural Frequency Analysis ◽  
The Relationship

The typical speaker for cellular phone is composed of magnet, coil, base-film and diaphragm with a structure that laminated a foam sheet and aluminum sheets. A heterogeneous foam sheet which has an uneven elastic modulus was used for a conventional diaphragm, and it reduced an acoustic performance of a conventional speaker. Recently a homogeneous and thin foam sheet was newly developed. The purpose of this study is to improve the acoustic characteristics of the micro speaker by changing thickness and foaming ratio of the newly developed foam sheet. Frequency characteristics and sound pressure level (SPL) were measured by changing foaming ratio of the foam sheet from 2.5 to 5.0 and thickness of the foam sheet from 0.15 mm to 0.30 mm. To clarify the relationship between the design parameter of foam sheet and the frequency characteristics of the micro speaker, natural frequency analysis using finite element method (FEM) was performed. The result of FEM analysis was also compared with the experimental result using a laser doppler velocimetry sensor. It was found that the widest reproducible frequency range was obtained when the foam sheet was used 0.30 mm of thickness and 5.0 of foaming ratio. The reproducible frequency range spread out 15% in comparison with that of a conventional micro speaker.

Modelling and Numerical Analysis for High Frequency Characteristics of Laminated Galfenol Based on Eddy-Current

2014 ◽  
Author(s):  
Yimin Tan ◽  
Zuguang Zhang ◽  
Jean Zu
Keyword(s):  
Eddy Current ◽  
High Frequency ◽  
Power Efficiency ◽  
Maxwell Equations ◽  
High Strain ◽  
Ferromagnetic Material ◽  
Frequency Characteristics ◽  
Frequency Range ◽  
Critical Criterion ◽  
The Relationship

Galfenol, a novel magnetostrictive and ferromagnetic material, has been employed in various applications because of the material’s outstanding mechanical properties. For high frequency applications, the energy loss of eddy-current is a critical criterion because this loss not only reduces the power efficiency for Galfenol material, but also rapidly generates large amounts of heat that can destabilize the system. While laminating ferromagnetic material has been proved to be an effective way that minimises eddy-current, the objective of this research is to investigate the laminated Galfenol material’s plausibility in high frequency applications. For the prescribed geometry, an accurate model for the generated eddy-current is derived based on the Maxwell equations. Combining a built magnetic coupled dynamic model, the relationship between the strain response and the applied magnetic field is derived under high frequency conditions. The simulative results of the laminated Galfenol rods are compared to those rods without laminations. The comparison shows that the laminated Galfenol rod exhibits a milder hysteresis than the non-laminated Galfenol rod. Furthermore, the laminated Galfenol rod is able to maintain a high strain output with a broader frequency range compared to the non-laminated Galfenol rod. This work proves that laminating Galfenol rods are capable of restricting the generation of eddy-current and improving high frequency characteristics significantly.

New aspects of power grid facilities personnel workplaces electromagnetic environment

2020 ◽  
Vol 60 (9) ◽  
pp. 569-574
Author(s):  
Nina B. Rubtsova ◽  
Sergey Yu. Perov ◽  
Olga V. Belaya ◽  
Tatiana A. Konshina
Keyword(s):  
Transmission Lines ◽  
Power Transmission ◽  
Power Grid ◽  
Spectral Characteristics ◽  
Ground Level ◽  
Frequency Characteristics ◽  
Frequency Range ◽  
Electromagnetic Environment ◽  
Limit Values ◽  
Special Assessment

Introduction. Electromagnetic safety of power grid facilities staff requires the exclusion of electromagnetic fields (EMF) harmful effects. EMF is evaluated by 50 Hz electric and magnetic fields (EF and MF) values in the framework of working conditions special assessment, and very rarely the analysis of the electromagnetic environment (EME) is carried out in depth. The aim of the study - EME hygienic assessment of power grid EHV facilities personnel workplace with adequate 50 Hz EF and MF levels evaluation as well as the analysis of EF and MF in the frequency range from 5 Hz to 500 Hz amplitude-frequency characteristics. Materials and methods. 50 Hz EF and MF values assessment was carried out on open switchgears (S) of substations and within sanitary breaks of 500 and 750 kV overhead power transmission lines (OTL). Measurements along to OTL trasses was performed using matrix-based method. Measurements and analysis of EF and MF values in 5-500 Hz frequency range amplitude-frequency characteristics were performed in the territory of 500 and 750 kV S. Results. Power frequency 50 Hz measurements results at 500 and 750 kV S ground-level personnel workplaces showed the presence of an excess of permissible limit values by EF intensity and the absence of an excess by MF. The measured EF values within 500 and 750 kV OTL sanitary gaps require limiting the working time of linemen due to the excess of the hygienic norms for full work shift, while the MP levels were almost completely within the standard values for persons not occupationally connected with electrical installations maintenance. MF and EE frequency range from 50 Hz to 500 Hz spectral characteristics analysis showed that 3rd harmonic percentage does not exceed 2.5% for EF and 6% for MF of the main level, the level of the 5th harmonic does not exceed 1% for EF and 3.5% for MF, the level of the 7th harmonic does not exceed 0.2% for EF and 0.8% for MF. These data show despite its low levels the contribution of MF different harmonics in a possible adverse impact on humane than EF corresponding harmonics. Conclusions. There was the confirmation of the previously justified use of the "matrix" scheme for of EF and MF values measurement along OTL routes. The relevance of to EF and MF all frequency components expos ure assessing possible health risk in extremely high voltage S territories and under OTL, based on international recommendations due to the lack of sanitary regulations in the Russian Federation for >50 Hz-30 kHz EF and MF, is shown.

Study on acoustic and flow-induced noise characteristics of L-shaped duct with a shallow cavity

2020 ◽  
Vol 68 (3) ◽  
pp. 209-225
Author(s):  
Masaaki Mori ◽  
Kunihiko Ishihara
Keyword(s):  
Air Conditioning ◽  
Sound Field ◽  
Frequency Range ◽  
Acoustic Characteristics ◽  
Inflow Velocity ◽  
Aerodynamic Sound ◽  
Noise Characteristics ◽  
Flow Induced Noise ◽  
Shallow Cavity ◽  
Conditioning Equipment

An aerodynamic sound generated by a flow inside a duct is one of the noise pro- blems. Flows in ducts with uneven surfaces such as grooves or cavities can be seen in various industrial devices and industrial products such as air-conditioning equipment in various plants or piping products. In this article, we have performed experiments and simulations to clarify acoustic and flow-induced sound characteris- tics of L-shaped duct with a shallow cavity installed. The experiments and simula- tions were performed under several inflow velocity conditions. The results show that the characteristics of the flow-induced sound in the duct are strongly affected by the acoustic characteristics of the duct interior sound field and the location of the shallow cavity. Especially, it was found that the acoustic characteristics were af- fected by the location of the shallow cavity in the frequency range between 1000 Hz and 1700 Hz.

scholarly journals Estimation of resistance force at steady-state sinkage for cylindrical wheel-typed lunar/planetary exploration rovers with function of push–pull locomotion

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Daisuke Fujiwara ◽  
Naoki Tsujikawa ◽  
Tetsuya Oshima ◽  
Kojiro Iizuka
Keyword(s):  
Steady State ◽  
Estimation Method ◽  
Planetary Exploration ◽  
Experimental Result ◽  
Resistance Force ◽  
Estimation Model ◽  
Loose Soil ◽  
Key Factor ◽  
The Relationship ◽  
Resistance Forces

Abstract Planetary exploration rovers have required a high traveling performance to overcome obstacles such as loose soil and rocks. Push-pull locomotion rovers is a unique scheme, like an inchworm, and it has high traveling performance on loose soil. Push-pull locomotion uses the resistance force by keeping a locked-wheel related to the ground, whereas the conventional rotational traveling uses the shear force from loose soil. The locked-wheel is a key factor for traveling in the push-pull scheme. Understanding the sinking behavior and its resistance force is useful information for estimating the rover’s performance. Previous studies have reported the soil motion under the locked-wheel, the traction, and the traveling behavior of the rover. These studies were, however, limited to the investigation of the resistance force and amount of sinkage for the particular condition depending on the rover. Additionally, the locked-wheel sinks into the soil until it obtains the required force for supporting the other wheels’ motion. How the amount of sinkage and resistance forces are generated at different wheel sizes and mass of an individual wheel has remained unclear, and its estimation method hasn’t existed. This study, therefore, addresses the relationship between the sinkage and its resistance force, and we analyze and consider this relationship via the towing experiment and theoretical consideration. The results revealed that the sinkage reached a steady-state value and depended on the contact area and mass of each wheel, and the maximum resistance force also depends on this sinkage. Additionally, the estimation model did not capture the same trend as the experimental results when the wheel width changed, whereas, the model captured a relatively the same trend as the experimental result when the wheel mass and diameter changed.

Remembering How to Forget: An Artist's Exploration of Sound

2001 ◽  
Vol 11 ◽  
pp. 65-69 ◽  
Author(s):  
Scanner
Keyword(s):  
Public Art ◽  
Cellular Phone ◽  
Sound Art ◽  
The Public ◽  
Electronic Sound ◽  
Significant Performance ◽  
The Relationship ◽  
Digital Landscape

This article is an introduction to the work of electronic sound artist Scanner, which explores the place of memory, the cityscape and the relationship between the public and the private within contemporary sound art. Beginning with a historical look at his CD releases a decade ago, the article explores his move from his cellular phone works to his more collaborative digital projects in recent times. With descriptions of several significant performance works, public art commissions and film soundtrack work, the piece explores the resonances and meanings with the ever-changing digital landscape of a contemporary sound artist.

The relationship between group velocity and phase velocity for finite, discrete observations

1977 ◽  
Vol 67 (5) ◽  
pp. 1249-1258
Author(s):  
Douglas C. Nyman ◽  
Harsh K. Gupta ◽  
Mark Landisman
Keyword(s):  
Phase Velocity ◽  
Group Velocity ◽  
The Other ◽  
Frequency Range ◽  
Finite Frequency ◽  
Discrete Observations ◽  
Practical Situation ◽  
Order Polynomial ◽  
Observational Errors ◽  
The Relationship

abstract The well-known relationship between group velocity and phase velocity, 1/u = d/dω (ω/c), is adapted to the practical situation of discrete observations over a finite frequency range. The transformation of one quantity into the other is achieved in two steps: a low-order polynomial accounts for the dominant trends; the derivative/integral of the residual is evaluated by Fourier analysis. For observations of both group velocity and phase velocity, the requirement that they be mutually consistent can reduce observational errors. The method is also applicable to observations of eigenfrequency and group velocity as functions of normal-mode angular order.

Study on Evaluation of Sound Speed in Duct With Tube Banks

2010 ◽  
Author(s):  
Kunihiko Ishihara
Keyword(s):  
Heat Exchanger ◽  
Resonance Frequency ◽  
Vortex Shedding ◽  
Sound Speed ◽  
Flow Direction ◽  
Fem Analysis ◽  
The Self ◽  
Resonance Phenomenon ◽  
Acoustic Characteristics ◽  
Tube Banks

As tube banks are set in a duct in a boiler and a heat exchanger, the resonance phenomenon or the self sustained tone are generated due to the interference between vortex shedding and the acoustic characteristics of the duct. It is necessary to know the resonance frequency of the duct, namely sound speed, for avoiding any trouble that may arise. In general, it is said that the sound speed decreases in the duct with tube banks and an evaluation formula is given. However, this formula is often used for the perpendicular direction of the flow. We wanted to know whether this formula would be able to be used for the flow direction and for various arrays of patterns or not. In this paper, the applicability of this expression is discussed by using FEM analysis and experiments.

scholarly journals Snow Stratigraphy and Water Equivalence Measured With an Active Microwave System

1980 ◽  
Vol 26 (94) ◽  
pp. 225-233
Author(s):  
D. A. Ellerbruch ◽  
H. S. Boyne
Keyword(s):  
Electromagnetic Scattering ◽  
Direct Determination ◽  
Snow Pack ◽  
Frequency Range ◽  
Microwave Radar ◽  
Snow Stratigraphy ◽  
Microwave System ◽  
The Relationship ◽  
System Operating

AbstractThis paper reports on research on the relationship between the electromagnetic scattering properties and physical properties of snow-pack. An FM-CW active microwave radar system operating in the frequency range 8-12 GHz is used to scatter electromagnetic radiation from surface and subsurface stratigraphic layers in the snow-pack. The amplitude of the scattered radiation as a function of depth in the snow-pack can be correlated with such physical characteristics as density, hardness, stratigraphy, and moisture content. A direct determination of snow-pack water equivalence can be made from these observations.

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