Using Sonic Crystal and Nonlinear. Medium. Dipen N. ... of Sonic crystal .... Sonic. Crystal. Inside FC-43. Highest. Lowest. Intensity. Color map. Intensity. 0 .5 1.0 ...
Broadband Ultrasound Propagation Using Sonic Crystal and Nonlinear Medium Dipen N. Sinha and Cristian Pantea Los Alamos National Laboratory Los Alamos, New Mexico, USA
ICA 2013 Montreal June 2013
Unidirectional Low-Frequency Sound Transmission Through Passive Wall as a Collimated Beam with High Bandwidth Underwater 200 kHz – 1 MHz (Sonar) Modulated with highfrequency carrier (fc)
Non-linear model KZK (Khokhlov-Zabolotskaya-Kuznetsov) nonlinear parabolic equation
Normalized Amplitude
0.8
∂ 2 p c0 ∂ 2 p 1 ∂p D ∂3 p β ∂2 p2 + = + + ∂z∂t ' 2 ∂r 2 r ∂r 2c0 3 ∂t ' 3 2 ρ 0 c0 3 ∂t ' 2
0.6
0.4
Used Texas KZK Code
0.2
0.0 0
20
40
60
80
100
120
140
160
180
Axial distance (mm)
200
Diffraction
Absorption
Parameters for KZK Model:
Primary frequencies: 2.85 and 3.1 MHz Median frequency: 2.95 MHz Median pressure of the primaries: 55 kPa; Source diameter (SC outside surface opposite the transducer): 20 mm;
FC-43 Properties:
β: 7.6; Density: 1850 kg/m3 ; Sound speed: 646 m/s ; Absorption parameter: 6.17 Nonlinear parameter (ratio of Rayleigh length and Shock length): 22.29.
Nonlinearity
Transmission Amplitude (relative units)
Experimental Sound Transmission – Reverse Direction Very low transmission 0.003
Sonic crystal band gap
0.002
Low pass filter
0.001
No measurable transmission
0.000 0.0
0.5
1.0
1.5
2.0
Frequency (MHz)
2.5
3.0
Profiles of the Sound Beam Exiting from the Device into Water Demodulated Signal
Difference Frequency: 300 kHz
Carrier: 2.95 MHz AM signal: 220 kHz
f1: 3.1 MHz; f2: 2.8 MHz
(a)
(b)
Conclusions • Sound transmission through a device in the frequency range (200-400 kHz) has been demonstrated by taking advantage of the band gap and band pass characteristics of a sonic crystal combined with a nonlinear medium, and a low pass filter. • The key to this device is the modulation of a high frequency carrier with the desired low frequency signal within the band pass region of the sonic crystal and subsequent demodulation of the signal in a nonlinear medium. • Neither the low frequency nor the high frequency carrier alone can pass through the device because of the band gap of the sonic crystal and a low pass filter. • The signal exiting from the device is in the form of a collimated beam • The sound transmission characteristics of the device is unidirectional except at very low frequency
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Sonic Crystal Transmission Characteristics Repeated Pattern
Tranmission Amplitude
1.0
0.8
0.6
0.4
0.2
0.0 0
1
2
3
4
Frequency (MHz)
5
6
Sonic Crystal transmission with and without going through nonlinear medium 1.0
SC + NL
0.8
Normalized Transmission
0.6 0.4 0.2
(a)
0.0 0.0
0.5
1.0
1.5
2.0
2.5
3.0
2.0
2.5
3.0
SC only
1.0 0.8 0.6 0.4 0.2
(b)
0.0 0.0
0.5
1.0
1.5
Frequency (MHz)
Frequency mixing due to resonance in sonic crystal liquid layer Liquid layer is acoustically nonlinear 0.1
