Intuition might tell us that rough surfaces on clothing would inhibit the speed of an olympic athlete. why is this line of thinking not true in some cases? how can controlled roughness actually promote speed?

We associate roughness with a greater coefficient of friction, then we think that rough surfaces on clothing would inhibit the speed of an Olympic athlete.  This is not always true because the amount of roughness might improve the way air pass through the fabric.  

One example of controlled roughness that actually promote speed are the dimples on golf balls. Dimples create turbulence around the ball, which sucks air to the ball, making its displacement easier and promoting its speed.

the frequency increases and decreases.

Explanation: According to doppler effect, the frequency of waves tends to increase as the source approaches and decrease as the source disappears.

The Doppler effect occurs when a source of waves and/or observer move relative to each other, resulting in the  observer measuring a different frequency of the waves than the frequency that the source is emitting.