observation of acoustic dirac-like cone and double zero refractive index
by：QY Precision 2019-10-07
Zero exponential material spreads sound without phase change, and has great potential in pre-wave and scattering engineering. Recently, a double zero exponential hypermaterial consisting of periodic scattering bodies has been found, and the refractive index of these scattering bodies is significantly greater than that of the surrounding medium. This requirement is basically challenging for airborne acoustics because of the sound speed ( Inversely proportional to the refractive index) The air is the slowest. Here, we report the impedance matching of the first experiment to the Dirac-caused by the sound double zero refractive index supermaterial- Like a cone in the center of the briyuan district. This is in two- Dimensional waveguide with periodically varying air channels for modulation of high- Order the wave catheter mode. Use such a zero Index media, we demonstrate the acoustic aiming emitted from the point light source. We confirmed for the first time in an experiment that- Like a cone in the center of the briyuan district. The band structure of the materials we designed is calculated using a commercial finite element solver. The design material contains a cylindrical air scatter with a radius of 8mm and a height of 14. 5 u2009 mm forms a square lattice with a lattice constant of 30 u2009 mm in two- Size 10mm thick air wave duct (). This wave catheter is formed by two acrylic plates on 930mm with an area of 540mm. 10 blind holes formed by 10 cylindrical scattering bodies are drilled by CNC machines. The spacers are placed in four corners of the wave duct, forming a 10mm thick air channel between the two acrylic plates. The wave ducts for the eight Unit units shown in the measurement are also manufactured by CNC machines. Two PUI AST-1532MR- The R speakers that produce the opposite phase of the airborne sound are assembled face-to-face on the top and bottom boards. They form an acoustic point light source at the center of our 10 × 10 unit samples that specifically stimulates the first-order waveguide mode. Acoustic signals are measured by cui cme-1538- 100LB microphone, amplified by Reson VP2000 voltage preamp ec6081. Stanford research system SR830 lock The amplifier is used to read the amplitude and phase of the sound signal. Two VELMEX MN10-0150- The E01 motor, controlled by the VXM stepping motor controller, is used to move the microphone and scan the acoustic field in the wave duct with a scan time of 75 by 60 points and a step size of 7. 6u2009mm. The authors state that all data supporting the results of this study can be found in the paper and its documents.