Sound Energy Harvesting Research Articles

Recent Advances in Acoustic Metamaterials for Simultaneous Sound Attenuation and Air Ventilation Performances

In the past two decades, acoustic metamaterials have garnered much attention owing to their unique functional characteristics, which are difficult to find in naturally available materials. The acoustic metamaterials have demonstrated excellent acoustical characteristics that paved a new pathway for researchers to develop effective solutions for a wide variety of multifunctional applications, such as low-frequency sound attenuation, sound wave manipulation, energy harvesting, acoustic focusing, acoustic cloaking, biomedical acoustics, and topological acoustics. This review provides an update on the acoustic metamaterials’ recent progress for simultaneous sound attenuation and air ventilation performances. Several variants of acoustic metamaterials, such as locally resonant structures, space-coiling, holey and labyrinthine metamaterials, and Fano resonant materials, are discussed briefly. Finally, the current challenges and future outlook in this emerging field are discussed as well.

Internet of Things for Noise Mapping in Smart Cities: State of the Art and Future Directions

Noise pollution has been an issue since ancient times. Recently, this problem has been exacerbated due to rapid population growth and urbanization. Noise mapping is a strategic action plan that visualizes the long-term and real-time noise pollution of our cities, industrial sites, and other regions of interest. This article first discusses the working principle of general model-based noise mapping and the lessons learned. Then, in-depth descriptions of the technical challenges and design issues of noise mapping using mobile crowdsensing and acoustic sensor networks are presented. Finally, we provide our insights for future research directions regarding artificial intelligence assisted noise prediction, constructive interference for multimedia transmission, and simultaneous noise sensing and sound energy harvesting as well as inaudible sound attacks and defense.

Vibration based energy harvesting system for mobile device charging

Nowadays most of the time humans spend in daily life on mobile phones but the thing that tends to get worried about is battery consumption as they run out quickly. We could not make important jobs such as emergency calls or send important documents when our phone battery runs out. This study represents vibration based sound energy is harvested to charge mobile phones using six piezoelectric sound transducers (PSTs) which converts sound energy to electrical energy. This paper proposed designing a low voltage sound energy harvesting circuit (SEHC) using PSTs. PSTs with SEHC is considered as an alternative power source to charge the smart phone battery, especially for remote area where power is unavailable. The SEHC consists of PSTs, non-controlled bridge rectifier circuit, filter, switch-mode open loop boost converter, charger circuit, and storage device at the output terminal. The complete SEHC has designed and simulated using Matlab Simulink software. The PSTs have been analyzed with different frequency and the output voltage of PSTs utilized as an input source to design SEHC. Finally, the results are generated at an output of 7.8 V DC from an input 1.05 V AC at 314 Hz through a SEHC using the PSTs, which suitable to charge smartphone battery efficiently.

Highly flexible all-nonwoven piezoelectric generators based on electrospun poly(vinylidene fluoride)

Acoustic energy is a sustainable and clean form of energy that is always being generated and wasted in our environment. Acoustic energy harvesting technology is a very promising substitute for fossil fuels and can serve as a suitable power supply for small electronic devices, owing to the high efficiency of piezoelectric devices. Thus, many studies have investigated the conversion of sound energy into electricity for power generation. In this study, we successfully fabricated an all-nonwoven polymer-based piezoelectric generator with a high acoustic energy conversion efficiency and high flexibility. A dispersion of single-walled carbon nanotubes (SWCNTs) was sprayed onto electrospun poly(vinylidene fluoride) (PVDF) webs to produce flexible and durable electrodes. The thickness and flexibility of the PVDF web used as the active piezoelectric layer were controlled by the spinning time. The effect of flexibility on frequency response, sound pressure response, output power, and energy harvesting characteristics was investigated by observing sound wave-induced vibration behavior and evaluating the output characteristics of the generators. The all-nonwoven polymer-based generator with the highest flexibility showed the highest output voltage overall due to its excellent vibration characteristics. Due to its effectiveness and durability suitable for acoustic energy harvesting, this all-nonwoven polymer-based generator can be useful for a wide range of applications, such as wearable electronics and large area flexible devices.

Sound Energy Harvesting Methods

This paper presents the various strategies and aspects of sound energy harvesting. We have discussed sound energy harvesting related to wireless sensor networks(WSNS) and regarding ultra low power requirements.

Compact acoustic metalens with sinusoidal sub-channels for directional far-field sound beams

A metasurface lens (i.e., metalens), composed of perforated sinusoidal channels evenly arrayed with sub-wavelength distances, is explored in this paper. Enhanced directional far-field sound transmission over a large frequency range was realized through using this compact metalens. Numerical simulations and experimental tests demonstrated a pronounced diffraction-limited sound beam from 7390 to 7600 Hz, which reached as far as 57.6 cm at 7551 Hz with a width of 9 cm. This metalens is a feasible candidate for directional sound projection and sound energy harvesting.

A brief review of sound energy harvesting

Sound energy harvesting is one of the promising technologies due to the abundant and clean sound sources. It can be the semi-permanent alternative power supplies for wireless sensor networks (WSNs), which is significant in the Internet of Things (IoT). However, sound waves have the low energy density, so there are many kinds of research in recent years to overcome this problem. This paper provides a comprehensive review of sound energy harvesting, focusing on presenting principles, examples and enhancement methods of sound energy harvesters. In this paper, various approaches are introduced which are classified as sound pressure amplification and transduction mechanism. For sound pressure amplification, two typical types of energy harvesters are presented that one is using a resonator, another one is using an acoustic metamaterial, and these are based on piezoelectric, electromagnetic, and triboelectric mechanisms to convert sound energy to electrical energy.

Simultaneous realization of large sound insulation and efficient energy harvesting with acoustic metamaterial

Acoustic metamaterials, capable of both sound insulation and energy harvesting, composed of Helmholtz resonators and built-in decorated membranes are proposed. It is theoretically and experimentally proved that the proposed metamaterial can obtain two sound insulation bands where the sound energy is also efficiently harvested at the same frequency simultaneously. The peak of the output power can reach up to 244 nW when the incident sound pressure is 1 Pa, which is about 14 times larger than structures composed of single membrane reported before with the same input. Moreover, considerable energy harvesting with average output power of about 20 nW can be achieved within wider frequency ranges (with bandwidth up to 90 Hz) by choosing proper parameters. Additionally, the hybrid resonance mechanism of the proposed metamaterials is explained well with an equivalent theoretical model. These novel properties of the proposed metamaterial can be applied in many potential applications in noise control and energy harvesting.

Analysis of batteries or supercapacitor as energy storage device for a sound energy harvester system

This study focuses on the concept analysis of the suitability of batteries or a supercapacitor as an alternative storage device in low‐power electronic devices. Sound waves were utilized as a source of energy for charging the supercapacitor, and a piezoelectric Q220‐A4‐503YB device was used as the energy transducer. A respectable performance of the piezoelectric in terms of the output force and voltage was found at the operating frequency of 68 Hz with an input source of 96 dB sound intensity level. Based on our experiments, it was found that the supercapacitor is more efficient as a storage device for a low‐power source when compared to batteries because of the charging current. The charging time of the 0.22‐F supercapacitor used in either the Villard or Dickson mode is higher when compared to the others. The charging time of the supercapacitor with the voltage regulator of 0.5 and 1.0 W by the Villard multiplier was longer compared to the Dickson multiplier, which produced an output voltage of 9.817 and 9.647 V, respectively. From this study, it is proven that the delivery of the voltage stored in a supercapacitor with a higher capacitance would take a longer time in terms of process charging and discharging as compared to one with a lower capacitance. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Analytical coupled modeling of a magneto-based acoustic metamaterial harvester

Membrane-type acoustic metamaterials (MAMs) have demonstrated unusual capacity in controlling low-frequency sound transmission, reflection, and absorption. In this paper, an analytical vibro-acoustic-electromagnetic coupling model is developed to study MAM harvester sound absorption, energy conversion, and energy harvesting behavior under a normal sound incidence. The MAM harvester is composed of a prestressed membrane with an attached rigid mass, a magnet coil, and a permanent magnet coin. To accurately capture finite-dimension rigid mass effects on the membrane deformation under the variable magnet force, a theoretical model based on the deviating acoustic surface Green’s function approach is developed by considering the acoustic near field and distributed effective shear force along the interfacial boundary between the mass and the membrane. The accuracy and capability of the theoretical model is verified through comparison with the finite element method. In particular, sound absorption, acoustic-electric energy conversion, and harvesting coefficient are quantitatively investigated by varying the weight and size of the attached mass, prestress and thickness of the membrane. It is found that the highest achievable conversion and harvesting coefficients can reach up to 48%, and 36%, respectively. The developed model can serve as an efficient tool for designing MAM harvesters.

The Design of Operational Amplifier for Low Voltage and Low Current Sound Energy Harvesting System

The objective of this paper is to design a combination of an operational amplifier (op-amp) with a rectifier used in an alternate current (ac) to direct current (dc) power conversion. The op-amp was designed to specifically work at low voltage and low current for a sound energy harvesting system. The goal of the op-amp design with adjustable gain was to control output voltage based on the objectives of the experiment conducted. The op-amp was designed for minimum power dissipation performance, with the means of increasing the output current when receiving a large amount of load. The harvesting circuits which designed further improved the power output efficiency by shortening the fully charged time needed by a supercapacitor bank. It can fulfil the long-time power demands for low power device. Typically, a small amount of energy sources were converted to electricity and stored in the supercapacitor bank, which was built by 10 pieces of capacitors with 0.22 F each, arranged in parallel connection. The highest capacitance was chosen based on the characteristic that have the longest discharging time to support the applications of a supercapacitor bank. Testing results show that the op-amp can boost the low input ac voltage (∼3.89 V) to high output dc voltage (5.0 V) with output current of 30 mA and stored the electrical energy in a big supercapacitor bank having a total of 2.2 F, effectively. The measured results agree well with the calculated results.

Sound Energy Harvester with Frequency Tunable Acoustic Metamaterial Cavity

We demonstrate a new type of acoustic harvester by utilizing an acoustic metamaterial cavity designed by double coiledup space like structures. In the case of double coiled-up metamaterials, high refractive index (n) miniaturizes the device at the subwavelength scale and high impedance (z) leads to efficient sound amplification rate inside the cavity, respectively. These miniaturized cavities enable to enhance the energy-convergence rate of acoustic harvester. When the resonant frequency of acoustic cavity coincides with the 1st natural frequency of the piezoelectric harvester, the amplification of sound pressure with 16dB sound pressure level gain leads to efficient acoustic mechanical-electrical conversion rate. Compared to acoustic harvesting method with only piezoelectric devices, experimental results illustrate that the proposed techniques exhibit six-time higher voltage output.

Sound energy harvesting using a doubly coiled-up acoustic metamaterial cavity

A new sound energy harvesting system that comprises an acoustic metastructure and a double-clamped piezoelectric bimorph plate is presented. A subwavelength-scale acoustic metastructure is specially designed by utilizing a doubly coiled-up configuration for the strong confinement of the sound energy inside the acoustic metamaterial cavity in the low frequency range. The amplified sound pressure in the acoustic metamaterial cavity then substantially increases the vibratory motions of the piezoelectric bimorph plate. For the purpose of generating more electricity from the sound, the resonant frequency of the acoustic metamaterial cavity is tuned to the fundamental frequency of the piezoelectric bimorph plate. The numerical and experiment results show that the proposed sound energy harvesting system increase a sound pressure level (SPL) by up to ∼16 dB, and yields an output voltage that is 6.32 times higher than that of the conventional piezoelectric energy harvesting plate. For the incident SPL of 100 dB, the maximum output power is measured as approximately 0.345 μW at a resonant frequency of 600 Hz.

Exploring Piezoelectric for Sound Wave as Energy Harvester

Abstract This paper presents the characteristic of piezoelectric for sound wave energy harvester. The sound level on piezoelectric is experimented at range of 35-100 dB. This range is comparable with ambience environmental human sound of level 50-100 dB. Piezoelectric type Q220-A4-503YB has been used as energy transducer. This type of piezoelectric has achieved a better performance in term of output power or voltage. The output of piezoelectric transducer is connected to 3 difference types of harnessing circuitry; Villard voltage multiplier, Dickson voltage multiplier and full-wave rectifier. The measured results of piezoelectric transducer with and without connected to external circuitry devices have attained a good agreement with expected theory within the frequency of interest. The piezoelectric transducer accomplished maximum power response of performance 33.133 dBuW at sound level of 96 dB. The Villard and Dickson voltage multipliers produced output voltage greater than full wave bridges which are 9.817 V, 9.593 V and 3.504 V respectively at 96 dB sound intensity level. The results show that the piezoelectric transducer connected to Villard voltage multiplier produced the best performance. The proposed sound wave energy harvester offer a better performance and able to replace the problematic battery in wireless signal network.

Charaterization of Differents Dimension Piezoelectric Transducer for Sound Wave Energy Harvesting

Abstract This paper presents an investigation on characterization of variety types of piezoelectric profile for a sound wave energy harvester system design. Energy harvesting systems based on the convention of environmental acoustic vibrations into electrical energy are increasingly being used for low voltage applications due to the reduction in power consumption of modern day systems. The varieties of piezoelectric transducer structures are targeted to resonate at the ambient frequency which is below 1 kHz. The experimented sound level of the piezoelectric is at the range of 35-100 dB. It is comparable with ambience environmental human sound of level 50-100 dB. It is found that the QB 220-A4-503YB type - has shown a better performance of output power and sound level value. An energy harvester of piezoelectric transducer accomplished constant stage with the maximum amplitude at sound level of 96 dB. The measured results of piezoelectric strip with and without connected to external harvesting circuit devices have attained a good agreement within the frequency of interest. The piezoelectric transducer accomplished maximum power response performance at the 96 dB and 33.133 dB (uW). The results show that the customs size of piezoelectric will affects the efficiencies of the transducers to harvest energy. The large size piezoelectric transducer is able to convert a higher mechanical energy from sound wave into electrical energy. The proposed sound energy harvester can be used to replace the existing battery as a power source in wireless sensor network system as they offer better performance at lower cost.

Acoustic metamaterials capable of both sound insulation and energy harvesting

Membrane-type acoustic metamaterials are well known for low-frequency sound insulation. In this work, by introducing a flexible piezoelectric patch, we propose sound-insulation metamaterials with the ability of energy harvesting from sound waves. The dual functionality of the metamaterial device has been verified by experimental results, which show an over 20 dB sound transmission loss and a maximum energy conversion efficiency up to 15.3% simultaneously. This novel property makes the metamaterial device more suitable for noise control applications.

Sound energy harvesting using an acoustic grating

A sound energy harvester with an acoustic grating and a piezoelectric plate has been demonstrated. The acoustic grating consists of a metal slit grating and a thin flat metal screen. The metal slit grating can squeeze an incident acoustic wave into the air gap between the slit grating and metal screen, thus giving rise to high sound pressure and causing the metal screen to vibrate. Using the direct piezoelectric effect, the “squeezed” acoustic energy is harvested efficiently by a piezoelectric component that is mounted on the back of the metal screen.

A novel flexible capacitive touch pad based on graphene oxide film

Recently, graphene oxide (GO) supercapacitors with ultra-high energy densities have received significant attention. In addition to energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as vibration and sound energy harvesting. Here, we experimentally create a macroscopic flexible capacitive touch pad based on GO film. An obvious touch "ON" to "OFF" voltage ratio up to ∼60 has been observed. Moreover, we tested the capacitor structure on both flat and curved surfaces and it showed high response sensitivity under fast touch rates. Collectively, our results raise the exciting prospect that the realization of macroscopic flexible keyboards with large-area graphene based materials is technologically feasible, which may open up important applications in control and interface design for solar cells, speakers, supercapacitors, batteries and MEMS systems.