Experimental study of smart sound absorber using multimode electromechanical coupling control in the low-frequency range

2021 ◽  
Vol 263 (3) ◽  
pp. 3800-3810
Author(s):  
Xiang Liu ◽  
Keming Wu ◽  
Lixi Huang
Keyword(s):  
Electromechanical Coupling ◽  
Electrical Response ◽  
Low Frequency ◽  
Design Procedure ◽  
Frequency Range ◽  
Acoustic Performance ◽  
Sound Absorber ◽  
Multiple Frequencies ◽  
Broadband Sound ◽  
Shunt Circuit

To construct a smart sound absorber in the low-frequency range with a wide control band, a piezoelectric ceramic (PZT) shunted with multiple resonance circuit is attached onto a micro-perforated panel (MPP) to perform as a smart sound absorber. The absorption can be controlled by the shunt circuit parameters conveniently. This smart micro-perforated panel (MPP) is investigated experimentally to explore the feasibility and design procedure in practical use. Based on the coupling among the acoustical, electrical, and mechanical fields, the proposed broadband sound absorber can achieve good acoustic performance on subwavelength scales. The electrical response of the shunt circuit is tested with a Network Analyzer. The acoustic performance of the smart sound absorber is measured in an impedance tube with the two-microphone transfer function method. The experimental results validate that the shunt circuit can resonate with the PZT patch at multiple frequencies, and hence improve the sound absorption of the smart absorber at these frequencies.

Optimally Sensitive and Efficient Compact Loudspeakers for Low Audio Frequencies

2007 ◽  
Vol 38 (7) ◽  
pp. 11-17
Author(s):  
Ronald M. Aarts
Keyword(s):  
Optimality Criterion ◽  
Low Frequency ◽  
Audio Signal ◽  
Design Procedure ◽  
Frequency Range ◽  
Force Factor ◽  
Low Frequencies ◽  
Limited Frequency ◽  
The Cost ◽  
Higher Sensitivity

Conventionally, the ultimate goal in loudspeaker design has been to obtain a flat frequency response over a specified frequency range. This can be achieved by carefully selecting the main loudspeaker parameters such as the enclosure volume, the cone diameter, the moving mass and the very crucial “force factor”. For loudspeakers in small cabinets the results of this design procedure appear to be quite inefficient, especially at low frequencies. This paper describes a new solution to this problem. It consists of the combination of a highly non-linear preprocessing of the audio signal and the use of a so called low-force-factor loudspeaker. This combination yields a strongly increased efficiency, at least over a limited frequency range, at the cost of a somewhat altered sound quality. An analytically tractable optimality criterion has been defined and has been verified by the design of an experimental loudspeaker. This has a much higher efficiency and a higher sensitivity than current low-frequency loudspeakers, while its cabinet can be much smaller.

Acoustic performance analysis of Helmholtz resonators with conical necks and its application

2019 ◽  
Vol 67 (3) ◽  
pp. 155-167 ◽  
Author(s):  
Haitao Liu
Keyword(s):  
Finite Element ◽  
Prediction Model ◽  
Transmission Loss ◽  
Low Frequency ◽  
Wide Band ◽  
Acoustic Properties ◽  
Frequency Range ◽  
Acoustic Attenuation ◽  
Acoustic Performance ◽  
Helmholtz Resonators

The acoustic properties of the Helmholtz resonators with conical necks, which have broad acoustic attenuation band performance in the low frequency range, are investigated in this study. In order to investigate its wide-band acoustic attenuation mechanism, three-dimensional finite element models for the Helmholtz resonators with different necks are built respectively. The acoustic performance prediction model based on the one-dimensional analytical approach with acoustic length corrections is built to calculate the transmission loss results more efficiently, and the formula for calculating the resonance frequency is also derived. Then, the prediction model and the formula are verified by finite element method and experiment, which show good agreements. As a result, the prediction model is applied to analyze the sound attenuation properties of the Helmholtz resonators with conical necks, and the results show that the acoustic attenuation bandwidth in the low frequency range is improved by increasing the taper angle of the neck. At last, the approaches for the Helmholtz resonators with conical necks are applied to design an actual middle silencer of a passenger car. The results show that the designed middle silencer performs much better than the original one, which can effectively eliminate the exhaust order noise to meet the standard of exhaust noise control. The test results fully reveal that the Helmholtz resonators with conical necks in the muffler can play a better role in eliminating exhaust order noise, and the approaches proposed in this article can effectively guide the design of Helmholtz resonators with conical necks.

scholarly journals Effect of Porous Materials Combination in Layers on Sound Absorption Characteristics

2015 ◽  
Vol 773-774 ◽  
pp. 210-215
Author(s):  
Muhd Hafeez Zainulabidin ◽  
M.H.M. Yusuff ◽  
Al Emran Ismail ◽  
M.Z. Kasron ◽  
A.S.M. Kassim
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Absorption Coefficient ◽  
Frequency Range ◽  
Sound Absorber ◽  
Number Of Layers ◽  
Combination Number ◽  
Impedance Tubes ◽  
Absorption Characteristics

This paper describes the investigation and analysis on two materials in which one material is a relatively good sound absorber at low frequency range and another is a relatively good sound absorber at high frequency range, combined together in layers to form a better sound absorber for a wider range of frequencies. The layer combinations of the materials are varied and the values of Sound Absorption Coefficient, α are measured experimentally by using impedance tubes with two microphones transfer function method according to ISO 10534-2 standard. The results obtained are compared in terms of the order of material and the number of layer combinations of materials for each sample. The orders of combinations and number of layers of combinations have significant influence on the sound absorption characteristics. The order of materials has reversed effect on Sound Absorption Coefficient, α as the number of layer combination is increased. Increase in the combination number will make the specimen performed relatively better at a wider frequency range.

Tunable Piezoelectric Cantilever Beams for Energy Harvesting

Aerospace ◽  
2006 ◽  
Author(s):  
David Charnegie ◽  
Changki Mo ◽  
Amanda A. Frederick ◽  
William W. Clark
Keyword(s):  
Cantilever Beam ◽  
Electromechanical Coupling ◽  
Mechanical Energy ◽  
Piezoelectric Element ◽  
Electrical Energy ◽  
Vibration Source ◽  
Frequency Range ◽  
Piezoelectric Cantilever ◽  
Tip Mass ◽  
Shunt Circuit

Over the past several years, there has been increasing interest in harvesting energy from ambient vibrations in the environment by converting mechanical energy into electrical energy. A popular method is to use a piezoelectric cantilever beam. In order to harvest the most energy with the device, the beam's fundamental mode must be excited. However, this is not always possible due to manufacturing of the device or fluctuations in the vibration source. By being able to change the frequencies of the beam, the device can be more effective in harvesting energy. In this paper, a model for a three layered piezoelectric cantilever beam utilizing a shunt tuning circuit will be presented. The fundamental frequency of a cantilever beam is dependent on the stiffness and mass of the beam. Either adding a tip mass to the end of the beam or increasing the dimensions of the beam can alter the mass. The stiffness of the beam is a function of the geometry, mechanical properties, and the electromechanical coupling of the piezoelectric element. In this paper we prepare the use of a piezoelectric layer with an attached shunt circuit for tuning its stiffness, and thus the beam frequency. The piezoelectric coefficients of this layer and its shunt circuit determine the amount of electromechanical coupling. By varying the shunt circuit, the beam can be tuned to a certain frequency. This paper presents a study of the effects additional harvesting and tuning layers have on the amount of tuning and generated power in the beam. These additional layers will add more piezoelectric material as well as mass to the beam and therefore there will be a balance between the amount of harvested energy and the tunable frequency range. By quantifying the effects of these parameters, it will be easier to design a harvester to be used in a particular frequency range as well as to produce a certain level of power.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

An hourglass-type electromagnetic isolator with negative resistance electromagnetic shunt circuit

2020 ◽  
Vol 64 (1-4) ◽  
pp. 549-556
Author(s):  
Yajun Luo ◽  
Linwei Ji ◽  
Yahong Zhang ◽  
Minglong Xu ◽  
Xinong Zhang
Keyword(s):  
Vibration Isolation ◽  
Electromechanical Coupling ◽  
Coupling Effect ◽  
Negative Resistance ◽  
Isolation System ◽  
Amplitude Vibration ◽  
Vibration Responses ◽  
The Stability ◽  
Isolation Performance ◽  
Shunt Circuit

The present work proposed an hourglass-type electromagnetic isolator with negative resistance (NR) shunt circuit to achieve the effective suppression of the micro-amplitude vibration response in various advanced instruments and equipment. By innovatively design of combining the displacement amplifier and the NR electromagnetic shunt circuit, the current new type of vibration isolator not only can effectively solve the problem of micro-amplitude vibration control, but also has significant electromechanical coupling effect, to obtain excellent vibration isolation performance. The design of the isolator and motion relationship is presented firstly. The electromechanical coupling dynamic model of the isolator is also given. Moreover, the optimal design of the NR electromagnetic shunt circuit and the stability analysis of the vibration isolation system are carried out. Finally, the simulation results about the transfer function and vibration responses demonstrated that the isolator has a significant isolation performance.

Dynamic Damping and Stiffness Characteristics of the Rolling Tire

2001 ◽  
Vol 29 (4) ◽  
pp. 258-268 ◽  
Author(s):  
G. Jianmin ◽  
R. Gall ◽  
W. Zuomin
Keyword(s):  
Dynamic Behavior ◽  
Variable Parameter ◽  
Low Frequency ◽  
Vertical Load ◽  
Frequency Range ◽  
Inflation Pressure ◽  
Vehicle Simulation ◽  
Dynamic Damping ◽  
Speed Range ◽  
Stiffness Characteristics

Abstract A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.

Highly Efficient Low‐Frequency Broadband Sound Absorption with a Composite Hybrid Metasurface

2021 ◽  
Author(s):  
Qingxuan Liang ◽  
Yutao Wu ◽  
Peiyao Lv ◽  
Jin He ◽  
Fuyin Ma ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Highly Efficient ◽  
Broadband Sound
Sign in / Sign up

Export Citation Format

Share Document