  We present a method for measuring internal stellar structure based on
asteroseismology that we call "inversions for agreement." The method accounts
for imprecise estimates of stellar mass and radius as well as the relatively
limited oscillation mode sets that are available for distant stars. By
construction, the results of the method are independent of stellar models. We
apply this method to measure the isothermal sound speeds in the cores of the
solar-type stars 16 Cyg A and B using asteroseismic data obtained from Kepler
observations. We compare the asteroseismic structure that we deduce against
best-fitting evolutionary models and find that the sound speeds in the cores of
these stars exceed those of the models.
