Broadband unidirectional transmission of sound in unblocked channel

We have designed and experimentally fabricated a straight channel capable of realizing unidirectional acoustic transmission within a broad band while leaving a gap much wider than the wavelength that may serve as a passage for other entities such as fluids or objects. This extraordinary feature stems from a distinctly different mechanism that directs the sound path asymmetrically by employing acoustic metasurfaces. The numerical and experimental results agree quite well with the theoretical predictions. Our scheme may open up avenue for the design of acoustic one-way devices and have potentials in various applications such as architectural acoustics or medical ultrasound. (C) 2015 AIP Publishing LLC.