I will discuss how the acoustic oscillations that propagate in the photon-baryon fluid during the first million years of the Universe provide a robust method for measuring the cosmological distance scale. The distance that the sound can travel can be computed to high precision and creates a signature in the late-time clustering of matter that serves as a standard ruler. Galaxy clustering results from the Sloan Digital Sky Survey reveal this feature, giving geometric distances to a wide range of redshifts and producing an accurate measurement of the abundance of dark energy. I will review our recent work on the theory and practice of the acoustic oscillation method and our latest cosmology results from SDSS-III on the expansion history of the Universe.