Frequency of sound has no impact on the speed of sound (which is ~343 m/s in the air at STP).
Consider sound to be waves (as is the correct assumption). When one hears a low frequency sound, fewer sound waves are passing by the listener in a finite period of time than are passing by when a high frequency sound is heard.
Think of the high frequency sound as being "more compressed" rather than "faster."
Best of luck!