Answer: Choose plants that are easily jostled by the breeze. These include ornamental grasses and weeping trees, which make a rustling noise as they sway. Some seed pods also rattle in the wind or when shaken manually; try love-in-the-mist (Nigella damascena), an annual that’s quick to grow from seed. (Its seed head is pictured here.)
You might plant some of these plants closer than normal to a pathway or the edge of a sitting area, so that as people walk by, they brush the leaves or stems and cause noise.
Also look to non-plant features for audible input to your sensory garden. A fountain or other water feature adds the sound of trickling water. Crunchy paving, such as pea gravel, makes noise as you walk across it. Don’t be quick to gather up fallen leaves—they add a crunching sound to your footsteps. Hang wind chimes throughout the garden. Set up a bird feeder, or plant berrying shrubs and trees to attract birds that will contribute sound with their movements and song.