Sound speed vs. acoustic radius for models with different radii and mixing lengths. The solid and dashed lines refer to stars with 50R_⊙ and 10R_⊙, respectively. The different colored lines indicate the different mixing lengths in the model. The bottom panel shows the fractional difference in the sound-speed profiles compared to the sound-speed profile for a mixing length of 1.7 as a function of the acoustic radius for the different-radii stars. Refer to Section 4.4.1 for plot interpretation.