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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. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the influence of slits on sound reduction index of double steel frame partitions with and without mineral wool in the cavity was examined. It was shown that the sound insulation of the partition is strongly dependent on the relative position of the slits on each steel frame. As could be expected, the reduction in sound insulation due to slits is lower in partitions without mineral wool in the cavity, since the effect of slits is more important in the case of partitions with high sound insulation. [Copyright &y& Elsevier]

Abstract: To avoid the undesirable effects of a faulty sealing of outlet boxes, it is common to insert a gypsum board layer in the middle of a double frame partition. In this paper, measured sound reduction index data for double frame partitions, with and without a gypsum board layer insert, are presented. The results obtained show that the sound insulation decreases at low frequencies due to the presence of the internal layer. The weighted sound reduction index, which is strongly affected by the low frequency sound insulation, decreases by 7–8dB. Since these degradations are greater than those resulting from small gaps in partitions, it can be concluded that the insertion of a gypsum board layer in the middle of a double frame partition is not a suitable solution to the undesirable effects of faulty sealing of outlet boxes. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]