Sound absorption based on Micro-perforated panels and Acoustic Black Hole principle

2021 ◽  
Vol 263 (6) ◽  
pp. 548-555
Author(s):  
Xiaoqi Zhang ◽  
Li Cheng
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Sound Absorption ◽  
Practical Application ◽  
Inner Radius ◽  
Simulation Results ◽  
Structural Configurations ◽  
Acoustic Black Holes ◽  
Sound Reduction ◽  
Bending Wave

Acoustic black holes (ABHs) have been so far investigated mainly for bending wave ma-nipulation in mechanical structures such as beams or plates. The investigations on ABHs for sound wave manipulation, referred to as Sonic black holes (SBHs) are scarce. Existing SBH structure for sound reduction in air is typically formed by putting a set of rings inside a duct wall with decreasing inner radius according to a power law. As such, the structure is very complex and difficult to be practically realized, which hampers the practical application of SBHs for sound reduction. This study explores the possibilities of achieving SBH effects using other types of structural configurations. In particular, micro-perforated panels are proposed to be introduced into the conventional SBH structure, and the simulation results show that the new formed SBH structure is simpler in configuration in terms of number of rings and more efficient in terms of sound energy trapping and dissipation.

scholarly journals QUASINORMAL MODES AND LATE-TIME TAILS OF CANONICAL ACOUSTIC BLACK HOLES

2007 ◽  
Vol 16 (07) ◽  
pp. 1211-1218 ◽  
Author(s):  
PING XI ◽  
XIN-ZHOU LI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Wave Propagation ◽  
Angular Momentum ◽  
Numerical Method ◽  
Time Scale ◽  
Quasinormal Modes ◽  
Late Time ◽  
Classical Wave ◽  
Acoustic Black Holes

In this paper, we investigate the evolution of classical wave propagation in the canonical acoustic black hole by a numerical method and discuss the details of the tail phenomenon. The oscillating frequency and damping time scale both increase with the angular momentum l. For lower l, numerical results show the lowest WKB approximation gives the most reliable result. We also find that the time scale of the interim region from ringing to tail is not affected obviously by changing l.

scholarly journals Superresonance phenomenon from acoustic black holes in neo-Newtonian theory

2016 ◽  
Vol 25 (05) ◽  
pp. 1650055 ◽  
Author(s):  
I. G. Salako ◽  
Abdul Jawad
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Sound Wave ◽  
Black Hole Mass ◽  
Newtonian Theory ◽  
Acoustic Black Holes ◽  
Bathtub Model

We explore the possibility of the acoustic analogue of a super-radiance like phenomenon, i.e. the amplification of a sound wave by reflection from the ergo-region of a rotating acoustic black hole in the fluid draining bathtub model in the presence of the pressure to be amplified or reduced in agreement with the value of the parameter [Formula: see text]. We remark that the interval of frequencies depend upon the neo-Newtonian parameter [Formula: see text] ([Formula: see text]) and becomes narrow in this work. As a consequence, the tuning of the neo-Newtonian parameter [Formula: see text] changes the rate of loss of the acoustic black hole mass.

scholarly journals A NOTE ON ACOUSTIC BLACK HOLES IN NEO-NEWTONIAN THEORY

2013 ◽  
Vol 28 (37) ◽  
pp. 1350169 ◽  
Author(s):  
J. C. FABRIS ◽  
O. F. PIATTELLA ◽  
H. E. S. VELTEN ◽  
I. G. SALAKO ◽  
J. TOSSA
Keyword(s):  
Fluid Dynamics ◽  
Black Holes ◽  
Black Hole ◽  
Newtonian Fluid ◽  
Pressure Effects ◽  
Inertial Effects ◽  
Newtonian Theory ◽  
Acoustic Black Holes

Newtonian fluid dynamics allows the construction of acoustic metrics from which black hole configurations can be studied. However, relativistic pressure effects are neglected within Newtonian theory. We study acoustic black holes in the framework of neo-Newtonian hydrodynamics, which is designed to take into account relativistic inertial effects of the pressure p. Within this new hydrodynamical context we show how p can influence the formation of the acoustic horizons.

Investigation on low-frequency broadband characteristics of three-dimensional acoustic black hole superstructures

2020 ◽  
Vol 34 (17) ◽  
pp. 2050151
Author(s):  
Zhuo Zhou ◽  
Xiao Liang ◽  
Jiu Hui Wu ◽  
Peng Shang ◽  
Jiamin Niu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Three Dimensional ◽  
Low Frequency ◽  
Sound Insulation ◽  
Frequency Range ◽  
Multi Stage ◽  
Two Samples ◽  
Acoustic Black Holes ◽  
Frequency Sound Wave

In order to solve the problem of strong penetration and difficult attenuation of low-frequency sound wave in traditional materials, several three-dimensional acoustic black hole superstructures are designed. First of all, multi-stage acoustic black holes are designed. It is found that their sound insulation coefficient is about 0.9 in the frequency range of 50–1600 Hz when the ration of the outlet tip diameter to the inlet diameter is [Formula: see text]. Then, the acoustic black hole thin and light superstructure was designed by embedding many acoustic black hole units in an array on the 10 mm thick plate. The sound insulation coefficient of two samples embedded 81 or 144 acoustic black holes is above 0.96 in the frequency range of 50–1600 Hz. To facilitate processing and engineering applications, we designed acoustic black hole wedge-shaped plate superstructures, and found that the average sound insulation of these acoustic black hole superstructures is 30 dB in the frequency range of 50–1600 Hz. These superstructures will be widely used in anechoic rooms, factories and aviation.

scholarly journals Thermodynamics of Acoustic Black Holes in Two Dimensions

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Baocheng Zhang
Keyword(s):  
Fluid Dynamics ◽  
Black Holes ◽  
Black Hole ◽  
Two Dimensions ◽  
Two Dimensional ◽  
Schwarzschild Black Hole ◽  
First Law Of Thermodynamics ◽  
Entropic Gravity ◽  
Acoustic Black Holes ◽  
Made In

It is well-known that the thermal Hawking-like radiation can be emitted from the acoustic horizon, but the thermodynamic-like understanding for acoustic black holes was rarely made. In this paper, we will show that the kinematic connection can lead to the dynamic connection at the horizon between the fluid and gravitational models in two dimensions, which implies that there exists the thermodynamic-like description for acoustic black holes. Then, we discuss the first law of thermodynamics for the acoustic black hole via an intriguing connection between the gravitational-like dynamics of the acoustic horizon and thermodynamics. We obtain a universal form for the entropy of acoustic black holes, which has an interpretation similar to the entropic gravity. We also discuss the specific heat and find that the derivative of the velocity of background fluid can be regarded as a novel acoustic analogue of the two-dimensional dilaton potential, which interprets why the two-dimensional fluid dynamics can be connected to the gravitational dynamics but it is difficult for four-dimensional case. In particular, when a constraint is added for the fluid, the analogue of a Schwarzschild black hole can be realized.

scholarly journals WHAT DID WE LEARN FROM STUDYING ACOUSTIC BLACK HOLES?

2002 ◽  
Vol 17 (20) ◽  
pp. 2721-2725 ◽  
Author(s):  
RENAUD PARENTANI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Hawking Radiation ◽  
Asymptotic Properties ◽  
Planck Scale ◽  
Density Fluctuations ◽  
Effective Theory ◽  
Linear Dispersion ◽  
Black Hole Evaporation ◽  
Acoustic Black Holes

The study of acoustic black holes has been undertaken to provide new insights about the role of high frequencies in black hole evaporation. Because of the infinite gravitational redshift from the event horizon, Hawking quanta emerge from configurations which possessed ultra high (trans-Planckian) frequencies. Therefore Hawking radiation cannot be derived within the framework of a low energy effective theory; and in all derivations there are some assumptions concerning Planck scale physics. The analogy with condensed matter physics was thus introduced to see if the asymptotic properties of the Hawking phonons emitted by an acoustic black hole, namely stationarity and thermality, are sensitive to the high frequency physics which stems from the granular character of matter and which is governed by a non-linear dispersion relation. In 1995 Unruh showed that they are not sensitive in this respect, in spite of the fact that phonon propagation near the (acoustic) horizon drastically differs from that of photons. In 2000 the same analogy was used to establish the robustness of the spectrum of primordial density fluctuations in inflationary models. This analogy is currently stimulating research for experimenting Hawking radiation. Finally it could also be a useful guide for going beyond the semi-classical description of black hole evaporation.

Hawking radiation of analogous acoustic black holes

2020 ◽  
Vol 35 (28) ◽  
pp. 2050236
Author(s):  
Shiwei Zhou ◽  
Kui Xiao
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Hawking Radiation ◽  
Emission Rate ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Spherically Symmetric ◽  
Sound Waves ◽  
Flowing Fluid ◽  
Acoustic Black Holes

Propagation of sound waves in a flowing fluid can be viewed as a minimally coupled massless scalar field propagating in curved spacetime. The analogue Hawking radiation from a spherically symmetric acoustic black hole and a (2 + 1)-dimensional rotating acoustic black hole are investigated respectively in Damour–Ruffini’s method. The emission rate and Hawking temperature are obtained, which are related to acoustic black holes parameter.

scholarly journals Acoustic Black Holes in Structural Design for Vibration and Noise Control

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 220-251 ◽  
Author(s):  
Chenhui Zhao ◽  
Marehalli Prasad
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Structural Design ◽  
Noise Control ◽  
Experimental Studies ◽  
Effective Control ◽  
Vibration Energy ◽  
Geometrical Parameters ◽  
Vibration Energy Harvesting ◽  
Acoustic Black Holes

It is known that in the design of quieter mechanical systems, vibration and noise control play important roles. Recently, acoustic black holes have been effectively used for structural design in controlling vibration and noise. An acoustic black hole is a power-law tapered profile to reduce phase and group velocities of wave propagation to zero. Additionally, the vibration energy at the location of acoustic black hole increases due to the gradual reduction of its thickness. The vibration damping, sound reduction, and vibration energy harvesting are the major applications in structural design with acoustic black holes. In this paper, a review of basic theoretical, numerical, and experimental studies on the applications of acoustic black holes is presented. In addition, the influences of the various geometrical parameters and the configuration of acoustic black holes are presented. The studies show that the use of acoustic black holes results in an effective control of vibration and noise. It is seen that the acoustic black holes have a great potential for quiet design of complex structures.

Superresonance effect and energy flow in acoustic black holes

2006 ◽  
Vol 84 (6-7) ◽  
pp. 501-506 ◽  
Author(s):  
R Kobes
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Energy Flow ◽  
Numerical Solutions ◽  
Kerr Black Hole ◽  
Scalar Fields ◽  
Acoustic Black Holes ◽  
Analogous Effect

We study numerically the superresonance effect of scalar fields incident on an acoustic black hole. We show that the superresonance effect is quite large compared with the analogous effect in a Kerr black hole. We also do an analysis of the energy flow from these numerical solutions to determine where the outward flow of energy originates.PACS Nos.: 11.10.–z, 04.70.–s

scholarly journals ACOUSTIC BLACK HOLES FROM SUPERCURRENT TUNNELING

2012 ◽  
Vol 21 (04) ◽  
pp. 1250038 ◽  
Author(s):  
XIAN-HUI GE ◽  
SHAO-FENG WU ◽  
YUNPING WANG ◽  
GUO-HONG YANG ◽  
YOU-GEN SHEN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Josephson Junction ◽  
Experimental Verification ◽  
Josephson Effect ◽  
Tunneling Current ◽  
Hawking Temperature ◽  
Middle Region ◽  
Superconducting Electronics ◽  
Acoustic Black Holes

We present a version of acoustic black holes by using the principle of the Josephson effect. We find that in the case where two superconductors A and B are separated by an insulating barrier, an acoustic black hole may be created in the middle region between the two superconductors. We discuss in detail how to describe an acoustic black hole in the Josephson junction and write the metric in the language of the superconducting electronics. Our final results infer that for big enough tunneling current and thickness of the junction, experimental verification of the Hawking temperature could be possible.

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