Board Thread:General Discussion/@comment-25372545-20141231084433/@comment-5398287-20141231150955

The speed of sound seems correct, given how the Arrancar's movement technique is the Spanish word for sound, and it's roughly equivalent to the other two in speed, and so on.

However, I'd posit that Shinigami, Arrancar, and Quincy with higher levels of proficiency in their respective speed techniques, e.g. Yoruichi, Starrk, and Yhwach, can go up to Mach 2 or even 3.