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.

The experimental study on low frequency sound transmission characteristics of the acoustic black hole

2019 ◽  
Vol 33 (36) ◽  
pp. 1950458 ◽  
Author(s):  
Xiao Liang ◽  
Zhuo Zhou ◽  
Jiu Hui Wu
Keyword(s):  
Black Hole ◽  
Low Frequency ◽  
Sound Transmission ◽  
Numerical Results ◽  
Acoustic Energy ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Transmission Characteristics ◽  
Acoustic Black Holes ◽  
Insulation Performance

The acoustic black hole has good sound insulation performance in low frequency range. The transmission and insulation characteristics of acoustic black hole is investigated by experiments. First, we study the transmission and insulation characteristics of the acoustic black hole by numerical simulation. Second, we studied the sound transmission characteristic of multi-level acoustic black hole. Finally, the sound transmission and insulation characteristics of the acoustic black hole are studied by experiments. The influence of the acoustic black hole tip’s diameter on sound insulation coefficient is studied. The sound transmission characteristics of the first, two and three level acoustic black holes are also studied by experiments. Our numerical results show that low frequency acoustic energy can be effectively focused at the tip of the acoustic black hole, and can be effectively insulated by the acoustic black hole. Our numerical results are verified by the experimental results. Our study can provide a feasible method for controlling the low frequency noise.

scholarly journals Note on acoustic black holes from black D3-brane

2019 ◽  
Vol 28 (07) ◽  
pp. 1950095 ◽  
Author(s):  
Chao Yu ◽  
Jia-Rui Sun
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Low Frequency ◽  
De Sitter ◽  
Hydrodynamic Description ◽  
Long Wavelength ◽  
Quasi Normal Mode ◽  
Holographic Approach ◽  
Acoustic Black Holes ◽  
Dynamical Connection

Black D3-branes are known to admit an effective hydrodynamic description when low frequency and long wavelength perturbations are introduced into the system. We use this perturbed nonextremal black D3-brane as background metric to study the emergence of acoustic black holes, following the same holographic approach in constructing the acoustic black hole in asymptotically Anti-de-Sitter (AAdS) background spacetime. We show that the acoustic black hole which appears on the timelike cutoff surface in the nonextremal black D3-brane also admits a holographic dual description. The duality includes the dynamical connection between the acoustic black hole and the bulk gravity, a universal equation relating the Hawking-like temperature and the real Hawking temperature, and a phonon/scalar channel quasi-normal mode correspondence.

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 Constraints on ultra-low-frequency gravitational waves with statistics of pulsar spin-down rates

2019 ◽  
Vol 489 (3) ◽  
pp. 3547-3552
Author(s):  
Hiroki Kumamoto ◽  
Yuya Imasato ◽  
Naoyuki Yonemaru ◽  
Sachiko Kuroyanagi ◽  
Keitaro Takahashi
Keyword(s):  
Black Hole ◽  
Gravitational Waves ◽  
Time Derivative ◽  
Low Frequency ◽  
Upper Bounds ◽  
Galactic Centre ◽  
Frequency Range ◽  
Rate Distribution ◽  
Black Hole Binaries ◽  
Supermassive Black Hole

Abstract We probe ultra-low-frequency gravitational waves (GWs) with statistics of spin-down rates of millisecond pulsars (thereafter MSPs) by a method proposed in our previous work. The considered frequency range is 10−12 Hz ≲ fGW ≲ 10−10  Hz . The effect of such low-frequency GWs appears as a bias to spin-down rates that has a quadrupole pattern in the sky. We use the skewness of the spin-down rate distribution and the number of MSPs with negative spin-down rates to search for the bias induced by GWs. Applying this method to 149 MSPs selected from the ATNF pulsar catalogue, we derive upper bounds on the time derivative of the GW amplitudes of $\dot{h} \lt 6.2 \times 10^{-18}~{\rm s}^{-1}$ and $\dot{h} \lt 8.1 \times 10^{-18}~{\rm s}^{-1}$ in the directions of the Galactic Centre and M87, respectively. Approximating the GW amplitude as $\dot{h} \sim 2 \pi f_{\rm GW} h$, the bounds translate into h < 3 × 10−8 and h < 4 × 10−8, respectively, for fGW = 1/(1000 yr). Finally, we give the implications to possible supermassive black hole binaries at these sites.

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.

Three-dimensional static black hole with Λ and nonlinear electromagnetic fields and its thermodynamics

2019 ◽  
Vol 28 (12) ◽  
pp. 1950160
Author(s):  
M. B. Tataryn ◽  
M. M. Stetsko
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Electromagnetic Fields ◽  
Three Dimensional ◽  
Nonlinear Electrodynamics ◽  
Extended Phase Space ◽  
Field Equations ◽  
Extended Phase ◽  
Dimensional Spacetime ◽  
Static Black Hole

Static black hole with the Power Maxwell invariant (PMI), Born–Infeld (BI), logarithmic (LN), exponential (EN) electromagnetic fields in three-dimensional spacetime with cosmological constant was studied. It was shown that the LN and EN fields represent the Born–Infeld type of nonlinear electrodynamics. It the framework of General Relativity the exact solutions of the field equations were obtained, corresponding thermodynamic functions were calculated and the [Formula: see text] criticality of the black holes in the extended phase-space thermodynamics was investigated.

scholarly journals On-axis scalar absorption cross section of Kerr–Newman black holes: Geodesic analysis, sinc and low-frequency approximations

2018 ◽  
Vol 27 (11) ◽  
pp. 1843012 ◽  
Author(s):  
Carolina L. Benone ◽  
Luiz C. S. Leite ◽  
Luís C. B. Crispino ◽  
Sam R. Dolan
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Rotation Axis ◽  
Low Frequency ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Absorption Cross ◽  
Newman Black Hole

We investigate null geodesics impinging parallel to the rotation axis of a Kerr–Newman black hole, and show that the absorption cross section for a massless scalar field in the eikonal limit can be described in terms of the photon orbit parameters. We compare our sinc and low-frequency approximations with numerical results, showing that they are in excellent agreement.

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.

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