Broadband acoustic triggers based on multiport waveguide structures

Abstract

The study of acoustic information processing has attracted great attention owing to its advantages of anti-electromagnetic interference and low energy consumption. Acoustic logic device, as a fundamental component, plays an important role in designing integrated acoustic systems. In the past few years, with the rapid development of sonic crystals, acoustic metamaterials and metasurfaces, researchers have demonstrated a variety of acoustic logic gates based on different mechanisms, and have devoted their efforts to the promotion of the practical applications. The more complex acoustic triggers with broad bandwidth and subwavelength size are very important for developing integrated sound devices, but it is difficult to realize them. In this work, we design two types of acoustic triggers based on the mechanisms of linear interference and phase modulation. The acoustic trigger with a width of 0.32<i>λ</i> and length of 0.82<i>λ</i> is composed of phased unit cells and multi-port waveguide structures, showing a subwavelength structure. Based on the phase modulation of the phased unit cells and the mechanism of linear interferences, the acoustic T-type trigger and D-type trigger with the same threshold are designed and demonstrated experimentally. The corresponding working bands of the T-type and D-type triggers are 3.293–4.069 kHz and 3.400–4.138 kHz, and their fractional bandwidths (the ratio of the bandwidth to the center frequency) can reach about 0.23 and 0.22, respectively, showing a broadband characteristic of both triggers. The mechanism of the T-type trigger is attributed to the linear interference caused by two phased unit cells with a phase difference of π. However, the realization of the D-type trigger is closely related to the incident sound energy and the phase modulation caused by the phased unit cell in the control port. The measured results and simulated results agree well with each other. Compared with other types of acoustic logic devices, the designed acoustic triggers have the advantages of broad bandwidth, subwavelength size, same threshold, and passive structure, as well as being easy to integrate, thus providing great potential applications in acoustic computing, acoustic communication, acoustic information processing and integrated acoustics. Our experimental demonstration of acoustic triggers can further promote the theoretical and experimental investigations of basic acoustic components.