Morphogenesis of sound creates acoustic rainbows

Sound is a crucial sensing element for many organisms in nature, with various species evolving organic structures that produce complex acoustic scattering and dispersion phenomena to emit and perceive sound clearly. To date, designing artificial scattering structures that match the performance of these organic structures has proven challenging. Typically, sound manipulation relies on active transduction in fluid media rather than passive scattering principles, as often observed in nature. In this work, we use computational morphogenesis to create complex, energy-efficient, wavelength-sized single-material scattering structures that passively decompose radiated sound into its spatio-spectral components. Specifically, we design an acoustic rainbow structure with "above unity" efficiency and an acoustic wavelength splitter. Our work demonstrates what is possible when using computational morphogenesis to tailor the emission and reception of sound fields, with relevance to disciplines concerned with the sensing and emission of wave fields.