Vicente Gómez-Lozano

Sound transmission through plates perforated with two periodic subwavelength hole arrays

Theoretical results on sound transmission through plates perforated with compound periodic hole arrays are presented. Calculations are obtained by means of a model under the rigid-solid assumption, which is thoroughly derived. A complex interplay between resonant transmission peaks, resonance interference, and Wood anomaly minima is observed. At high frequencies the resonant peaks overcome the Wood anomaly dips, leading to a different behaviour when compared with simple hole arrays.

Subwavelength slit acoustic metamaterial barrier

Reduction of noise in the transmission path is a very important environmental problem. The standard method to reduce this noise level is the use of acoustic barriers. In this paper, an acoustic metamaterial based on sound transmission through subwavelength slits, is tailored to be used as an acoustic barrier. This system consists of two rows of periodic repetition of vertical rigid pickets separated by a slit of subwavelength width, embedded in air. Here, both the experimental and the numerical analyses are presented. These analyses have facilitated the identification of the parameters that affect the insertion loss performance. The results demonstrated that the proposed barrier can be tuned to mitigate a band noise in a mechanical plant for buildings where openings for air flow are required as well as industrial noise, without excessive barrier thickness.

Ultrasonic lens based on a subwavelength slit surrounded by grooves.

The lensing capabilities of a single subwavelength slit surrounded by a finite array of grooves milled into a brass plate is presented. The modulation of the beam intensity of this ultrasonic lens can be adjusted by varying the groove depth. Numerical simulations as well as experimental validations at 290 kHz are shown. The experimental results are in good agreement with the numerical simulations. This system is believed to have potential applications for medical ultrasound fields such as tomography and therapy.

A tunable acoustic barrier based on periodic arrays of subwavelength slits

The most usual method to reduce undesirable enviromental noise levels during its transmission is the use of acoustic barriers. A novel type of acoustic barrier based on sound transmission through subwavelength slits is presented. This system consists of two rows of periodic repetition of vertical rigid pickets separated by a slit of subwavelength width and with a misalignment between them. Here, both the experimental and the numerical analyses are presented. The acoustic barrier proposed can be easily built and is frequency tunable. The results demonstrated that the proposed barrier can be tuned to mitigate a band noise without excesive barrier thickness. The use of this system as an environmental acoustic barrier has certain advantages with regard to the ones currently used both from the constructive and the acoustical point of view.

Ultrasonic transmission through multiple-sublattice subwavelength holes arrays.

The ultrasonic transmission through plates perforated with 2 × 2 or 3 × 3 square array of subwavelength holes per unit cell are studied by numerical simulations. Calculations are obtained by means of a theoretical model under the rigid-solid assumption. It is demonstrated that when the inter-hole distance within the unit cell is reduced, new transmission dips appear resulting from Wood anomalies that have influence on the second and the third order Fabry-Perot peak. When the inter-hole distance within the unit cell is reduced, the transmission spectrum of the multiple-sublattice holes arrays tends to the transmission spectrum of a plate perforated with only one hole in the unit cell.

Geometrical isotropy in perforated plates with subwavelength holes decorated with Archimedean patterns

The design and use of small apertures perforated in opaque plates to control the transmission of ultrasonic waves has been widely studied in recent years. The ultrasonic transmission response of brass plates perforated with Archimedean patterns of subwavelength hole arrays immersed in water is reported, both numerically and experimentally, in this work. It is shown that an increase in the geometrical isotropy of the elementary cells of the Archimedean patterns gives rise to a suppression of both minimum and maximum transmission corresponding to the destructive and constructive interferences, leading to uniformity within the angle-dependent transmitted sound power coefficient. The experimental results are in close agreement with the calculated ones. This property can be used to design ultrasonic devices such as filters and sensors.

Ultrasonic transmission through plates perforated with compound hole arrays

Numerical results obtained under the rigid-solid assumption are presented for compound arrays as a function of both parallel-to-plate wave-vector and frequency. Transmission minima arising from the interference between hole resonances interact with Wood anomalies. In addition, preliminary results on underwater ultrasound transmission measurements through a plate perforated with a rectangular hole array employing single point and synthetic aperture technique are presented.

Sound Insulation of Lightweight Partitions with Circular Apertures with Varying Overlap

A simple prediction model is developed to predict the decrease in sound reduction index in single and double frame lightweight partitions with the space between gypsum boards filled mineral wool and with circular apertures. The calculation model shows how the distance between centres of the circular apertures on each side of the partition affects the sound reduction index of the whole partition. Calculated results are compared with measured ones. In general, the prediction model developed shows good agreement with the measured results.