DE-based capacitive micro-speakers for generating directional audible sound

2020 ◽  
Vol 234 (10) ◽  
pp. 1325-1334
Author(s):  
Mohammad Soosani ◽  
Mohammad Fathalilou ◽  
Ghader Rezazadeh ◽  
Mohammad Homaei
Keyword(s):  
Smart Materials ◽  
Sound Pressure ◽  
Poor Performance ◽  
Fast Response ◽  
Deformation Energy ◽  
Dielectric Elastomer ◽  
Sound Waves ◽  
Micro Electro Mechanical Systems ◽  
Audible Sound ◽  
Human Hearing

Although silicon is the most used material in micro-electro-mechanical-systems, due to the excellent mechanical properties, it has poor performance for generating audible sound by capacitive micro-speakers. This paper studies the capability of dielectric elastomer material instead for generating the directional sound in the human hearing regime. Dielectric elastomers are a branch of smart materials with high desired and practical specifications such as large deformation, energy-efficient, lightweight, biocompatible, and fast response which share the common characteristics of changing their shape under an applied electrical voltage or charge. An elastic circular dielectric elastomer micro-plate with compliant electrodes on both sides suspended over the unmoving plate as a capacitive micro-structure has been modeled as a diaphragm of the micro-speaker. Then the Bessel panel array has been considered in a square matrix form composed of the number of dielectric elastomer micro-speakers. The nonlinear equation of the vibrations of a micro-speaker’s diaphragm under an electrostatic loading and equations of the sound pressure and sound radiation pattern have been presented and solved. The results have shown that utilizing dielectric elastomer-based micro-speakers in a Bessel panel array can generate a directional audible sound pressure in the human hearing range. In addition, the results clear that the desired sound waves in the human audible range and a private or personal listening zone can be produced through adopting an optimal value among the excitation frequencies, diaphragm numbers, radii and inter-element spaces of a Bessel panel array.

Application of the Electrostatic Micro-Speakers for Producing Audible Directional Sound

2020 ◽  
Vol 12 (04) ◽  
pp. 2050045
Author(s):  
Mohammad Homaei ◽  
Mohammad Fathalilou ◽  
Rasoul Shabani ◽  
Ghader Rezazadeh
Keyword(s):  
Radiation Pattern ◽  
Mechanical Systems ◽  
Sound Radiation ◽  
Sound Power ◽  
Sound Waves ◽  
Radiation Patterns ◽  
Micro Electro Mechanical Systems ◽  
Hearing Range ◽  
Human Hearing ◽  
Square Array

In recent years, the demand for control of sound power and radiation patterns in personal messaging, calls, automotive entertainment, and gaming has brought a new interest in the audio world. The aim of this paper is to investigate the feasibility of producing the sound waves in the audible range and directing them in the desired listening zone by electrostatic micro-speakers. Therefore, a capacitive circular micro-plate has been modeled as an electrostatic micro-speaker. Then a Bessel panel array has been developed using a number of these plates arranged in a square array. The equations governing the vibrations of the micro-speaker’s diaphragm, as well as radiation pattern of the sound waves, have been introduced and solved. The results have shown that the Micro-Electro Mechanical Systems (MEMS) electrostatic diaphragms have the capability of producing the directional sound in the human hearing range. Moreover, we have investigated the effect of different excitation frequencies, radii size and the number of the diaphragms as well as the inter-element spacing on the sound radiation pattern of the Bessel panel array.

Interaction between Strong Sound Waves and Cloud Droplets: Theoretical Analysis

2021 ◽  
Author(s):  
Ying-Hui Jia ◽  
Fang-Fang Li ◽  
Kun Fang ◽  
Guang-Qian Wang ◽  
Jun Qiu
Keyword(s):  
Sound Wave ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sound Field ◽  
Pressure Level ◽  
Velocity Variation ◽  
Time Range ◽  
Sound Waves ◽  
Cloud Droplets ◽  
Acoustic Frequency

AbstractRecently strong sound wave was proposed to enhance precipitation. The theoretical basis of this proposal has not been effectively studied either experimentally or theoretically. Based on the microscopic parameters of atmospheric cloud physics, this paper solved the complex nonlinear differential equation to show the movement characteristics of cloud droplets under the action of sound waves. The motion process of individual cloud droplet in a cloud layer in the acoustic field is discussed as well as the relative motion between two cloud droplets. The effects of different particle sizes and sound field characteristics on particle motion and collision are studied to analyze the dynamic effects of thunder-level sound waves on cloud droplets. The amplitude of velocity variation has positive correlation with Sound Pressure Level (SPL) and negative correlation with the frequency of the surrounding sound field. Under the action of low-frequency sound waves with sufficient intensity, individual cloud droplets could be forced to oscillate significantly. The droplet smaller than 40μm can be easily driven by sound waves of 50 Hz and 123.4 dB. The calculation of the collision process of two droplets reveals that the disorder of motion for polydisperse droplets is intensified, resulting in the broadening of the collision time range and spatial range. When the acoustic frequency is less than 100Hz (@ 123.4dB) or the Sound Pressure Level (SPL) is greater than 117.4dB (@ 50Hz), the sound wave can affect the collision of cloud droplets significantly. This study provides theoretical perspective of acoustic effect to the microphysics of atmospheric clouds.

Sound speed in pulmonary parenchyma

1983 ◽  
Vol 54 (1) ◽  
pp. 304-308 ◽  
Author(s):  
D. A. Rice
Keyword(s):  
Lung Volume ◽  
Sound Speed ◽  
Sulfur Hexafluoride ◽  
Ambient Pressure ◽  
Linear Regression Analysis ◽  
Free Field ◽  
Average Density ◽  
Sound Waves ◽  
Gas Phases ◽  
Audible Sound

The time it takes audible sound waves to travel across a lobe of excised horse lung was measured. Sound speed, which is the slope in the relationship between transit time and distance across the lobe, was estimated by linear regression analysis. Sound-speed estimates for air-filled lungs varied between 25 and 70 m/s, depending on lung volume. These speeds are less than 5% of sound speed in tissue and less than 20% of sound speed in air. Filling the lung with helium or sulfur hexafluoride, whose free-field sound speeds are 970 and 140 m/s, respectively, changed sound speed +/- 10% relative to air filling. Reducing the ambient pressure to 0.1 atm reduced sound speed to 30% of its 1-atm value. Increasing pressure to 7 atm increased sound speed by a factor of 2.6. These results suggest that 1) translobar sound travels through the bulk of the parenchyma and not along airways or blood vessels, and 2) the parenchyma acts as an elastic continuum to audible sound. The speed of sound is given by c = (B/rho)1/2, where B is composite volumetric stiffness of the medium and rho is average density. In the physiologic state B is affected by ambient pressure and percent gas phase. The average density includes both the tissue and gas phases of the parenchyma, so it is dependent on lung volume. These results may be helpful in the quantification of clinical observations of lung sounds.

scholarly journals IMPROVEMENT OF MUFFLER S DESIGN FOR REDUCTION OF THE LEVEL OF SOUND PRESSURE ON SMALL TRACTORS OPERATORS

2021 ◽  
Author(s):  
M. I. Podolsky ◽  
◽  
I. Y. Lilevman ◽  
O. Y. Lilevman ◽  
O. Y. Kedrovsky ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Gas Flow ◽  
Sound Pressure ◽  
Internal Combustion ◽  
Pressure Level ◽  
Combustion Engines ◽  
Sound Waves ◽  
Exhaust Gases ◽  
Noise Absorption ◽  
Made In

Noise background, as an important factor in the working conditions of agricultural operators, has a direct impact on human health and productivity. This topic is especially relevant for small tractors, which in most cases are not equipped with cabs. One of the main means of reducing the sound pressure on the operator are the mufflers of exhaust gases, which mainly have a labyrinth-absorbing type of action. The paper proposes a fundamental approach to the design of the muffler by the criterion of reflection and scattering of sound waves with the verification of efficiency by computer simulation. The purpose of research: - to improve the working conditions of operators of small tractors that are not equipped with cabs, by reducing the sound pressure level from internal combustion engines; - to improve the noise-absorbing properties of mufflers of exhaust gases of engines with observance of requirements to manufacturability of process of their manufacturing; - to develop a structural scheme of the exhaust gases muffler based on the results of preliminary modeling and analysis of the trajectory of the gas flow in the cavity of its working part. Methods. Determination of the sound pressure level of the engine of a small tractor by mathematical (computer) modeling of the behavior of the exhaust gas flow in the muffler cavity in different frequency ranges. Results. The article analyzes the main sources of noise during the operation of agricultural machinery with internal combustion engines (ICE). On the basis of literature sources and methods, their separate degree of influence on the complex picture of noise pollution of the working space of the operator of a small tractor is established. A comparative analysis of the efficiency of mufflers, created on the generally accepted principles and approaches to the design of such devices. According to the results of previous tests, shortcomings and limitations in the application of design concepts were identified, an additional analysis of external causes and factors was made, and adjustments were made to the method of creating muffler designs. An alternative design approach to the creation of internal combustion engine mufflers of small tractors is proposed and computer modeling of the processes of sound pressure distribution and sound waves in their cavity is performed. Conclusions. 1. A layout diagram of the design of the exhaust muffler, containing a resonator chamber and a shell module, which is made in the form of a three-stage ribbed diffuser of oscillations of the exhaust flow pulses with an additional surface layer of the vibration absorber. The parameters of the exhaust flow of exhaust gases of a typical diesel engine of a small tractor with a capacity of 24 hp are calculated. (pressure - 11652 Pa, acceleration – 90-105 m / s2, frequency - 1950-3300 Hz), which performed computer simulations of the process of gas movement in the muffler cavity of the proposed layout. Optimal design parameters were selected to ensure the maximum possible noise absorption with a body diameter of 150 mm and a length of 600 mm. The calculated sound pressure when working at the crankshaft speed (1700-2000) rpm does not exceed 72 dB. At the same time, the design of the muffler is made in compliance with the requirements for economic feasibility, manufacturability and in accordance with the capabilities of industrial production. A further direction of research is the manufacture of an experimental sample of the muffler and testing for the efficiency of its noise absorption in the conditions of operation of small tractors.

Comparison of Sound Pressure Level of Conventional and Modified Mufflers by using CFD Analysis

2021 ◽  
Vol 8 (01) ◽  
pp. 63-67
Author(s):  
Zahoor Ullah ◽  
◽  
Hassan Ahmed ◽  
Kareem Akhtar ◽  
◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Combustion Engine ◽  
Pressure Level ◽  
Destructive Interference ◽  
Cfd Analysis ◽  
Sound Waves ◽  
Reflected Waves ◽  
Engine Cylinder ◽  
Real Challenge

The reduction of noise emitted from the exhaust of internal combustion engine is a real challenge for all automotive industries. Mufflers are designed to reflect sound waves produced by the engine in such a way to cancel the effect of each other by destructive interference between the incoming waves from engine cylinder and reflected waves from the muffler of the 2 stroke motorbike engine. Numerical simulation is carried out to study the sound pressure level (SPL) and flow variable like velocity and pressure of conventional and proposed modified reactive muffler.

Dielectric Elastomer as a New Material for Electrostatically Actuated Microbeams: Stability Analysis

2019 ◽  
Vol 11 (10) ◽  
pp. 1950098
Author(s):  
Mohammad Fathalilou ◽  
Pegah Rezaei-Abajelou ◽  
Afsoon Vefaghi ◽  
Ghader Rezazadeh
Keyword(s):  
Pitchfork Bifurcation ◽  
Dielectric Elastomer ◽  
Micro Electro Mechanical Systems ◽  
High Deformation ◽  
Electrostatically Actuated ◽  
Eigen Value ◽  
Deformation Ability ◽  
New Material ◽  
The Stability ◽  
Stability Regime

Due to the interesting properties such as light weight and high deformation ability, dielectric elastomer (DE) resonators can be good alternatives for conventional silicon resonant beams used in micro-electro-mechanical systems (MEMS). This paper proposes a modeling in which a pre-stretched clamped-clamped DE-based microbeam oscillating above the ground substrate is subjected to an external electrostatic pressure. Using a DE-based beam affects the total rigidity of the system, which may lead to an anticipated saddle-node or pitchfork bifurcation. Hence, the present study tries to analyze the effects of DE properties on changing the stability regime of DE-based microbeams under electrostatic actuation. The stability of the system has been investigated using an eigen-value form of the problem. The effects of DE properties including pre-stress, relative permittivity and voltage value across the electrodes on pull-in or divergence instability as well as the frequency response of the system have been investigated. Moreover, the critical values of the DE voltage as a booster of instability occurrence have been obtained in either the presence or absence of the direct current (DC) voltage. It has been found that the pre-stress and appropriate DE permittivity can provide a needed magnitude of the DE actuating voltage to alter the resonance frequency and stability positions of the structure.

scholarly journals Validation of Nanoparticle Response to the Sound Pressure Effect during the Drug-Delivery Process

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 186 ◽  
Author(s):  
Mohamed Abbas ◽  
Mohammed Alqahtani ◽  
Ali Algahtani ◽  
Amir Kessentini ◽  
Hassen Loukil ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Sound Pressure ◽  
Pressure Effect ◽  
Experimental Results ◽  
Sound Waves ◽  
Subcutaneous Injections ◽  
Acrylic Plastic ◽  
Sound Pressure Levels ◽  
The Impact ◽  
Interaction Behaviors

Intravenous delivery is the fastest conventional method of delivering drugs to their targets in seconds, whereas intramuscular and subcutaneous injections provide a slower continuous delivery of drugs. In recent years, nanoparticle-based drug-delivery systems have gained considerable attention. During the progression of nanoparticles into the blood, the sound waves generated by the particles create acoustic pressure that affects the movement of nanoparticles. To overcome this issue, the impact of sound pressure levels on the development of nanoparticles was studied herein. In addition, a composite nanostructure was developed using different types of nanoscale substances to overcome the effect of sound pressure levels in the drug-delivery process. The results demonstrate the efficacy of the proposed nanostructure based on a group of different nanoparticles. This study suggests five materials, namely, polyimide, acrylic plastic, Aluminum 3003-H18, Magnesium AZ31B, and polysilicon for the design of the proposed structure. The best results were obtained in the case of the movement of these molecules at lower frequencies. The performance of acrylic plastic is better than other materials; the sound pressure levels reached minimum values at frequencies of 1, 10, 20, and 60 nHz. Furthermore, an experimental setup was designed to validate the proposed idea using advanced biomedical imaging technologies. The experimental results demonstrate the possibilities of detecting, tracking, and evaluating the movement behaviors of nanoparticles. The experimental results also demonstrate that the lowest sound pressure levels were observed at lower frequency levels, thus proving the validity of the proposed computational model assumptions. The outcome of this study will pave the way to understand the interaction behaviors of nanoparticles with the surrounding biological environments, including the sound pressure effect, which could lead to the useof such an effect in facilitating directional and tactic movements of the micro- and nano-motors.

Uses of ultrasonic cleaners in paleontological laboratories

1989 ◽  
Vol 4 ◽  
pp. 213-217 ◽  
Author(s):  
John Pojeta ◽  
Marija Balanc
Keyword(s):  
Mechanical Energy ◽  
Electrical Energy ◽  
Soft Materials ◽  
Low Pressure ◽  
Pressure Waves ◽  
Sound Waves ◽  
Ultrasonic Cleaning ◽  
Cleaning Solution ◽  
Rubber Cloth ◽  
Human Hearing

Ultrasonic cleaning is a fast and usually safe method for cleaning many hard objects that are not glued together, and it is thus useful in paleontological laboratories. It is relatively ineffective for cleaning soft materials such as rubber, cloth, and fibers. Ultrasonic cleaning machines use sound waves, or mechanical vibrations, that are above the human hearing range, and operate at frequences up to 55,000 cycles per second. The sound waves are generated by a transducer (Figure 1), which changes high frequency electrical energy to mechanical energy. This mechanical energy, or vibration, is then coupled into the liquid in the cleaning tank. The vibrations cause alternating high and low pressure waves in the liquid. This action forms millions of microscopic bubbles, which expand during low pressure waves and form small cavities. During the high pressure waves, these cavities collapse, or implode, creating a mechanical scrubbinglike action, which loosens dirt on all surfaces in contact with the cleaning solution. This action can take place up to 55,000 times a second, making it seem as though the dirt is being blasted from the surface and cavities of the object being cleaned. Ultrasonic cleaning is effective wherever capillary action will take the solution. Complete cleaning usually requires from 30 seconds to two minutes (Anonymous, 1983).

Multi-Functional Soft Smart Materials and their Applications

2011 ◽  
Vol 410 ◽  
pp. 25-25
Author(s):  
Jin Song Leng
Keyword(s):  
Smart Materials ◽  
Ph Value ◽  
Shape Memory Polymer ◽  
Soft Materials ◽  
Aerospace Engineering ◽  
Artificial Muscles ◽  
Automobile Engineering ◽  
Micro Electro Mechanical Systems ◽  
Morphing Aircraft ◽  
Space Deployable Structures

Stimulus-active polymers can change their shapes with respect to configuration or dimension upon exposure to a particular stimulus such as heat, electricity, light, magnetic, solvent and pH value. These unique characteristics enable stimulus-active polymers to be used in a myriad of fields, including clothing manufacturing, automobile engineering, medical treatment, and aerospace engineering. Stimulus-active polymers can be applied in smart textiles and apparels, intelligent medical instruments and auxiliaries, artificial muscles, biomimetic devices, heat shrinkable materials for electronics packaging, micro-electro-mechanical systems, self-deployable sun sails in spacecrafts, miniature manipulator, actuators and sensors, and many more. This paper presents some recent progress of soft smart materials and their applications. Special emphasis is focused upon shape memory polymer (SMP), electro-active polymer (EAP) for aerospace engineering such as space deployable structures and morphing aircraft, which has highlighted the need for development of these materials. A detailed overview of development in these smart soft materials, of which the undergoing and future applications are used in adaptive structures and active control, is presented. The paper concludes with a short discussion for multi-functional soft smart materials and their composites that are expected to extend the range of development and applications available to the related researches and engineers.

Bio-Inspired Soft Swim Bladders of Large Volume Change Using Dual Dielectric Elastomer Membranes

2020 ◽  
Vol 87 (4) ◽  
Author(s):  
Yingxi Wang ◽  
Leon Yeong Wei Loh ◽  
Ujjaval Gupta ◽  
Choon Chiang Foo ◽  
Jian Zhu
Keyword(s):  
Volume Change ◽  
Large Volume ◽  
Vertical Motion ◽  
Fast Response ◽  
Dielectric Elastomer ◽  
Control Mechanisms ◽  
Swim Bladder ◽  
Response Light ◽  
Large Volume Change ◽  
Buoyancy Control

Abstract The buoyancy control mechanism is critical for undersea robots to achieve effective vertical motion. However, current buoyancy control mechanisms are associated with problems such as complex design, bulky structure, noisy operation, and slow response. Inspired by the swim bladder of natural fish, we develop an artificial swim bladder, using dual membranes of the dielectric elastomer, which exhibit interesting attributes, including fast response, light weight, silent operation, especially large volume change. Both the experiments and theoretical simulations are conducted to analyze the performance of this artificial swim bladder, and they quantitatively agree with each other. This artificial swim bladder of dual membranes is capable of large voltage-induced volume change, 112% larger than the conventional single-membrane design. Consequently, this soft actuator can generate a buoyancy force of 0.49 N. This artificial swim bladder demonstrates effective up-and-down motion in water, due to its large reversible volume change. Future work includes adding horizontal-motion and turning capabilities to the existing robotic structure, so that the soft robotic fish can achieve successful navigation in undersea environments.

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