Sonic Crystals: Fundamentals, characterization and experimental
techniques A. Ceb recos
1 L a u m , L e M a n s U n i v e r s i t é , C N R S , A v. O . M e s s i a e n , 7 2 0 8 5 , L e M a n s
L A U M : J . P. G r o b y, V. R o m e r o - G a r c í a
U P V: N . J i m é n e z , V. S á n c h e z - M o r c i l l o , L . M . G a r c í a - R a f f i
U C B : M . H u s s e i n , D . K r a t t i g e r
Col lab orators in t h i s work:
Outline
• Part I ◦ Introduction to Sonic Crystals
◦ Origins and fundamentals
◦ Bandgaps. Dispersion relation.
◦ Group and phase velocities.
◦ Dispersion.
◦ EFC
◦ Methods for Dispersion Relation calculation
◦ Plane Wave expansion
◦ Finite-elements for band structure calculation in time-domain
• Part II ◦ Experimental techniques for the characterization of Sonic Crystals
◦ Dispersion relation using Space-time to frequency-wavevector transformation
◦ Methodology
◦ 2D Experimental relation using SLatCow
◦ Deconvolution method for analysis of reflected fields by SCs
◦ Methodology
◦ Practical application: Sonic Crystals for noise reduction at the launch pad
EXPERIMENTAL TECHNIQUES FOR THE CHARACTERIZATION OF SONIC CRYSTALS 2
A crystal is a solid material whose constituents, such as atoms, molecules or ions, are arranged in a highly ordered microscopic structure, forming a lattice that extends in all directions
Photonic crystal
E. Yablonovitch. PRL, 58, 2059, (1987).
Engineer photonic density of states to
control the spontaneous emission of
materials
embedded in the photonic crystal.
S. John. PRL, 58, 2486, (1987).
Using photonic crystals to affect localisation
and control of light.
Phononic crystal
Sonic crystal
Periodic distribution of solid scatterers in a solid host
medium
M. M. Sigalas and E. N. Economou. JSV. 158, 377. (1992)
M. S. Kushwaha et al,. PRL, 71, 2022. (1993)
Particular case in which the host medium is a fluid.
R. Martínez-Sala. Nature, 378. 241. (1995).
M. S. Kushwaha. APL, 70, 3218. (1997)
J. V. Sánchez-Pérez, PRL, 80, 5325. (1998)
E. Yablonovitch et al. PRL, 67, 2295, (1991).
Definition and origins
General definition: (Solid state physics)
Artificial (or even natural) materials whose physical properties are periodic functions of the space (1D, 2D, 3D)
Optical properties (electromagnetic waves) Dielectric constant (refractive index)
Elastic properties (elastic and acoustic waves) Density and elastic constants (speed of sound)
The study of photonic, phononic and sonic crystals makes use of the same concepts and theories developed in quantum mechanics for electron motion:
Direct and reciprocal lattices, Brillouin zone, Bragg interferences, Bloch periodicity, band structures…
ORIGINS AND FUNDAMENTALS
Direct Space
•
• There is a unique one-dimensional (1D) periodic system. • Five two-dimensional (2D). • Fourteen three-dimensional (3D) different lattices
• Unit cell and lattice constant
• Filling fraction
• Scatterer shape
Geometrical parameters
ORIGINS AND FUNDAMENTALS
2D Square lattice
•
Reciprocal Space
The reciprocal space (k-space) is used to study the wave propagation characteristics in periodic structures (Dispersion relation, bandgaps, propagation direction):
ORIGINS AND FUNDAMENTALS
•
Reciprocal Space
The study of the band structure can be limited to the Irreducible Brillouin zone. For the case of a square lattice the IBZ is reduced to a triangle.
The scatterer should accomplish the same symmetries in the direct space
ORIGINS AND FUNDAMENTALS
Direct and Reciprocal Space
• Direct space • Reciprocal space
Propagation pressure fields, Vibrational modes Band structures, Equifrequency contours, surfaces
ORIGINS AND FUNDAMENTALS
Origins and interpretation of the band gaps: Bragg interferences
J. D. Joannopoulos (Photonic crystals: Molding the flow of
light)
Illustration of Evanescent behaviour, 1D
E. Yablonovitch,. Scientific American,
285. (6). Dec. 2001, pp. 47-55
Bragg interferences
BANDGAPS. DISPERSION RELATION
Evidence of evanescent modes inside the BG
BANDGAPS. DISPERSION RELATION
V. Romero-García et al,. Appl. Phys. Lett., 96, 124102, (2010)
V. Romero-García et al,. J. Appl. Phys. 108, 044907, (2010)
Analytical, numerical and experimental results
Origins of the band gaps
Plane wave propagating in a 1D homogeneous medium
BANDGAPS. DISPERSION RELATION
• w(k) in homogeneous medium
Origins of the band gaps
Plane wave propagating in a 1D homogeneous medium
BANDGAPS. DISPERSION RELATION
• Periodicity in real space periodicity in reciprocal space
Origins of the band gaps
Plane wave propagating in a 1D homogeneous medium
BANDGAPS. DISPERSION RELATION
• Periodic w(k) repetitions of period 2pi/a (replicated bands due to periodicity)
Origins of the band gaps
Plane wave propagating in a 1D periodic medium
BANDGAPS. DISPERSION RELATION
• Periodic variation of the physical properties of the medium
Origins of the band gaps
Plane wave propagating in a 1D periodic medium
BANDGAPS. DISPERSION RELATION
• Creation of bandgaps and dispersion
Origins of the band gaps
BANDGAPS. DISPERSION RELATION
• Band gap frequency and dependence of its width
Plane wave propagating in a 1D periodic medium
2D Dispersion relation
BANDGAPS. DISPERSION RELATION
Plane wave propagating in a 2D homogeneous medium
• w(k) in 2D is now a surface
• Periodicity in x and y directions. Main directions of simmetry in reciprocal space
2D Dispersion relation
Plane wave propagating in a 2D homogeneous medium
BANDGAPS. DISPERSION RELATION
• Dispersion relation along the main simmetry points of the reciprocal space
2D Dispersion relation
BANDGAPS. DISPERSION RELATION
Plane wave propagating in a 2D homogeneous medium
2D dispersion relation
BANDGAPS. DISPERSION RELATION
• Periodic variation of the physical properties. Creation of pseudo gaps for low ff
Plane wave propagating in a 2D periodic medium
2D dispersión relation
BANDGAPS. DISPERSION RELATION
• Increasing ff and/or impedance contrast will eventually create a full band gap
Plane wave propagating in a 2D periodic medium
•
Phase and group velocities
DISPERSION. GROUP AND PHASE VELOCITIES
Group velocity and phase velocity
DISPERSION. GROUP AND PHASE VELOCITIES
Source: Institute of Sound and Vibration Research. University of Southampton
• Negative group velocity: Certain frequencies in the second band
Group velocity and phase velocity
DISPERSION. GROUP AND PHASE VELOCITIES
Source: Institute of Sound and Vibration Research. University of Southampton
• Higher phase velocity: Dispersive part of first band
Group velocity and phase velocity
• Zero group velocity: Localized wave
DISPERSION. GROUP AND PHASE VELOCITIES
Source: Institute of Sound and Vibration Research. University of Southampton
Understanding dispersion
• Group velocity
• Phase velocity
25
Plane wave propagating in a 1D periodic medium
DISPERSION. GROUP AND PHASE VELOCITIES
N = 200 layers
Rigid boundary conditions
Gaussian pulse at wn = 0.4
Understanding dispersion
• Group velocity
• Phase velocity
26
Plane wave propagating in a 1D periodic medium
DISPERSION. GROUP AND PHASE VELOCITIES
N = 200 layers
Rigid boundary conditions
Gaussian pulse at wn = 0.7
Understanding dispersion
• Group velocity
• Phase velocity
27
Plane wave propagating in a 1D periodic medium
DISPERSION. GROUP AND PHASE VELOCITIES
N = 200 layers
Rigid boundary conditions
Gaussian pulse at wn = 1
Equifrequency contours
DISPERSION. GROUP AND PHASE VELOCITIES
Generally considering infinite media by applying periodic boundary conditions (Bloch theory) PERIODIC : INFINITE MEDIUM
• Transfer matrix method (TMM)
• Plane wave expansion (PWE)
• Multiple scattering method (MST)
• Finite element method (FEM)
• Finite difference in time domain(FDTD)
• Finite element in time domain (FETD)
CHARACTERISTICS
• Dimensionality: 1D,2D,3D (TMM 1D, PWE, FEM, FDTD all, etc.)
• Handling different media (limitations in PWE solid-fluid except rigid inclusions in air or holes in solid matrix )
• Handling geometry (structure factor in PWE, meshing in FEM or FDTD)
• Steady-state or time dependent
29 METHODS FOR DISPERSION RELATION CALCULATION
Methods for dispersion relation calculation
PWE. Eigenvalue problem
Wave equation (inhomogeneous medium)
Considering a periodic medium
Fourier series
expansion The solution of a wave equation with periodic
potential can be written in the form:
Bloch’s theorem
PLANE WAVE EXPANSION
• Plane wave expansion (PWE)
PWE. Eigenvalue problem
Structure factor
Consider that the periodic structure is made of two materials, A and B, being B the host
material
Other shapes Square Cylinder
V. Romero-García. JPD, 40. 305108.
(2013)
R. Wang et al, JAP, 90, 2001
Hexagonal, rectangular, elliptic
• Model the shape of the scatterer:
Kushwaha et al., PRB, 49. (1994)
PLANE WAVE EXPANSION
PWE. Eigenvalue problem
PLANE WAVE EXPANSION
• Finite element in time-domain for elastic band structure calculation (FETD) ◦ Time-dependent Bloch periodicity
◦ Excitation required
• Continuum Equation of motion:
Finite element method in time-domain
Strong form general elastodynamic problem
Space Discretization
A. Cebrecos et al. The finite-element method for elastic band structure calculation. Computer Physics Communications. Under review
FINITE-ELEMENTS FOR BAND STRUCTURE CALCULATION IN TIME-DOMAIN
Unit-cell finite-element model
• Weak form:
Direct stiffness method Element to global
Bloch theory (BC’s) Option: Eigenvalue problem or time-integration (forced term)
Weighting and shape functions
FINITE-ELEMENTS FOR BAND STRUCTURE CALCULATION IN TIME-DOMAIN
Unit-cell time-domain simulation
• Time integration method:
◦ Center difference Newmark scheme (Explicit) ◦ Computationally efficient
◦ Less storage compared to implicit methods
◦ Conditionally stable
CFL
FINITE-ELEMENTS FOR BAND STRUCTURE CALCULATION IN TIME-DOMAIN
Unit-cell time-domain simulation
• Transient excitation ◦ Ricker wavelet
• Calculation of frequency band structure
FINITE-ELEMENTS FOR BAND STRUCTURE CALCULATION IN TIME-DOMAIN
Unit-cell time-domain simulation
• Transient excitation ◦ Ricker wavelet
• Calculation of frequency band structure
FINITE-ELEMENTS FOR BAND STRUCTURE CALCULATION IN TIME-DOMAIN
Numerical examples. Bloch Modeshapes
FINITE-ELEMENTS FOR BAND STRUCTURE CALCULATION IN TIME-DOMAIN
Dispersion relation using Space-time to frequency-wavevector transformation
PART I I
39
• Space-Time Fourier Transformation
1D Dispersion relation recovery: Methodology
40 DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
1D periodic medium
• Spatial sampling
1D Dispersion relation recovery
41
1D periodic medium
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
• What is the right spatial sampling measuring periodic structures?
• Using analogy from temporal signals:
• From Nyquist sampling theorem, considering periodicity in reciprocal space:
• Finally, consider a SC of a given length:
1D Dispersion relation recovery
42
Lattice constant
N° unit cells
For smaller dx, greater N
N° UNIT CELLS DEFINES RESOLUTION in k-space
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
1D Dispersion relation recovery
• Influence of SC size, undersampling and oversampling space
43 DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
Number of Unit cells Undersampling Oversampling
2D Dispersion relation recovery: Methodology
• 2D Acoustic metamaterial ◦ Quarter-wave resonators as scatterers (Lossless)
◦ 50 x 50 unit cells
◦ 50 measurement points in center line
◦ Point source at the center
44
Angular components in all directions
Bands overlapping
Dispersion relation incomplete!
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
2D Dispersion relation recovery: Methodology
• 2D Acoustic metamaterial ◦ Quarter-wave resonators as scatterers (Lossless)
◦ 50 x 50 unit cells
◦ 50 measurement points in center line
◦ Plane wave excitation
45
New angular components created due to scattering
Dispersion relation incomplete!
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
2D Dispersion relation recovery: Methodology
• Spatial “filtering” in the reciprocal space (k-space)
1. 1 measurement point per scatterer
2. Transformation to k-space (2D)
3. Selection of main symmetry directions for frequencies of interest
46
Isofrequency contours
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
2D Dispersion relation recovery: Methodology
• Spatial “filtering” in the reciprocal space (k-space)
• Results using a point source
47 DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
2D Dispersion relation recovery: Methodology
48 DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
• Spatial “filtering” in the reciprocal space (k-space)
• Results using a plane wave
Experimental dispersion relation measurement
• SLaTCow method: Complex dispersion relation
49
A. Geslain et al., J. Appl. Phys. 120,135107,
(2016) Wednesday morning at SAPEM
• Set of parameters defining theoretically the propagatio: amplitude, phase, real and imaginary part of the wave vector
• Optimization minimizing the difference between
and
Analysis for every frequency
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
Experimental dispersion relation measurement
• SLaTCow method: Complex dispersion relation
50
• Set of parameters defining theoretically the propagatio: amplitude, phase, real and imaginary part of the wave vector
• Optimization minimizing the difference between
and
Analysis for every frequency
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
Experimental dispersion relation
51
◦ 24 x 4 unit cells
◦ 1 measurement point per scatterer
Numerical results Experiments
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
Experimental dispersion relation
52
◦ 24 x 4 unit cells
◦ 1 measurement point per scatterer
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
Experimental dispersion relation
53
◦ 24 x 4 unit cells
◦ 1 measurement point per scatterer
DISPERSION RELATION USING SPACE-TIME TO FREQUENCY-WAVEVECTOR TRANSFORMATION
Deconvolution method for analysis of reflected fields by SCs
PART I I
54
Experimental evaluation of a SC Impulse Response
• Context of the problem: ◦ Study feasibility of Sonic Crystals in reducing impact of the backward
reflected field emitted by a sound source in a simplified scaled model of a launch pad (Proof of concept)
• Requisites (Greatly simplified problem): ◦ Linear regime
◦ Static source
◦ Broadband frequency study
◦ Scaled model in water (ultrasonic regime)
• Challenge: ◦ Analysis of reflected field by a SC
◦ Insertion loss in reflection
◦ Diffusion coefficient
ESA – ITI Type A project: Sonic Crystals for Noise Reduction at the Launch Pad
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
Experimental evaluation of a SC Impulse Response
ESA – ITI Type A project: Sonic Crystals for Noise Reduction at the Launch Pad
• Context of the problem: ◦ Study feasibility of Sonic Crystals in reducing impact of the backward
reflected field emitted by a sound source in a simplified scaled model of a launch pad (Proof of concept)
• Requisites:
◦ Linear regime
◦ Static source
◦ Broadband frequency study
◦ Scaled model in water (ultrasonic regime)
• Challenge: ◦ Analysis of reflected field by a SC
◦ Insertion loss in reflection
◦ Diffusion coefficient
Sound source
Reflector: • Sonic crystal • Rigid reflector
Ground surface
Areas of interest
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
•
Linear and time invariant system: Theory
Transfer function H(f):
• Widely used in experiments using SC’s
• Calculation of reflection, transmission and absorption coefficients
• Insertion Loss in attenuation devices
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
•
Linear and time invariant system: Theory
Impulse response h(t):
• Room acoustics: Acoustic quality parameters
• Weakly nonlinear system identification
• Incident and reflected pressure field
Farina A, Fausti P. Journal of Sound
and Vibration 2000;232(1):213-29
A. Novak, et al., IEEE Transactions on. Vol. 63(8), pp. 2044-2051. (2014)
Farina, A. Audio Engineering Society Convention 108. Audio Engineering Society, 2000.
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Input signal: Logarithmic sine sweep:
• Quasi-ideal case 1:
Impulse response deconvolution: Practical example
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Input signal: Logarithmic Sine sweep:
• Quasi-ideal case 2:
Impulse response deconvolution: Practical example
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Signal parameters
Experimental setup
Computer. Labview for measurement
control
DAQ-PXI Digital Signal Generator
Digital oscilloscope RF Amplifier
3D Motorized axis
Hydrophone
Piezoelectric transducer
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Input signal: Logarithmic Sine sweep:
• Real case: ◦ System response + reflections
Impulse response deconvolution: Example
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Input signal: Logarithmic Sine sweep:
• Real case: ◦ System response + reflections
Impulse response deconvolution: Example
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Characteristics of the SCs ◦ Four different samples (2D SCs)
◦ Square shape scatterers
◦ Square and triangular lattice
◦ Low and filling fraction
◦ 3D Printed ◦ Selective laser melting
Samples used in the experiments
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Experimental results: Incident field f = 700 kHz
Second Band
Incident and reflected field separation
f = 350 kHz
First Band f = 500 kHz
Band Gap
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
f = 700 kHz
High Band
• Reflected field. Square lattice High filling fraction
Incident and reflected field separation
f = 350 kHz
Low Band f = 500 kHz
Band Gap
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
Experimental wave propagation. Convolution signal on demand
67
• Input: Sinusoidal pulse (Narrow bandwidth, band gap)
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
68
Experimental wave propagation
• Input: Sinusoidal pulse (Narrow bandwidth, 2° Band)
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
Insertion loss results
69
• Modified Insertion loss to study reflection
• IL along the space integrated in frequency
Reduction of the reflected field depending on the reflection angle
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
Insertion loss results
70
• Modified Insertion Loss to study reflection
• IL in frequency bands integrated in ROI
Reduction of the reflected field due to diffusion Higher in propagative bands Lower in the BG
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Near to far field transformation
◦ Projection of the pressure in near to field to infinity ◦ Esentially it is a spatial Fourier transform
◦ Angular information
Difussion coefficient
71
T. J. Cox, P. D'antonio. Acoustic absorbers and diffusers: theory, design and application. Crc Press, 2009.
Reflection from a flat rigid surface
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Diffusion coefficient
• Normalized diffussion coeficient
• Quantification of the type of reflection
◦ Specular
◦ Diffuse
Difussion coefficient
72
ISO 17497-2:2012 Acoustics -- Sound-scattering properties of surfaces -- Part 2: Measurement of the directional diffusion coefficient in a free field
DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
• Far field results
• Normalized diffussion coeficient
• Normalized diffussion coeficient
• Quantification of the type of reflection
◦ Specular
◦ Diffuse
Difussion coefficient results
73 DECONVOLUTION METHOD FOR ANALYSIS OF REFLECTED FIELDS BY SCS
Sonic Crystals: Fundamentals, characterization and experimental
techniques A. Ceb recos
1 L a u m , L e M a n s U n i v e r s i t é , C N R S , A v. O . M e s s i a e n , 7 2 0 8 5 , L e M a n s
L A U M : J . P. G r o b y, V. R o m e r o - G a r c í a
U P V: N . J i m é n e z , V. S á n c h e z - M o r c i l l o , L . M . G a r c í a - R a f f i
U C B : M . H u s s e i n , D . K r a t t i g e r
Col lab orators in t h i s work:
Positive, zero and negative diffraction.
• Focusing of waves using finite SC’s:
◦ Curvature of the wave front
◦ Character of the incident wave
◦ Plane wave
◦ Point source
◦ Sound beam (Gaussian beam) ◦ Width of the source
D=2a
D=8a
DISPERSION. GROUP AND PHASE VELOCITIES
Isofrequency contours & Focusing regimes
• Focusing of waves using finite SC’s:
– Interplay between beam and periodic media
• Band structure and Isofrequency contours (PWE)
• Spatial spectrum of the incident beam
a = 5,25 mm r = 0,8 mm
D=2a
D=8a
Extended BZ
Source angular spectrum
Isofrequency contour
Band structure
DISPERSION. GROUP AND PHASE VELOCITIES
• Spatial dispersion completely parabolic
Results
Accumulated phase shift
Focusing distance
D=8a
D=2a
DISPERSION. GROUP AND PHASE VELOCITIES