Methods and devices for increasing the sound attenuation properties of a noise suppression device are provided. Various embodiments include sound-attenuating cavities with improved sound capturing openings. In some embodiments, the sound capturing openings include holes surrounded by projections. In other embodiments, the sound capturing openings include angled slats. Embodiments also include sound capturing devices that include the improved sound capturing openings, such as silencers, vent hoods, barrier walls, air exchanges, and air intake and exhaust ducts.