Doppler shift moving parallel to wall Suppose you are screaming and running in an area parallel to a wall. What would be the frequency you hear considering that you are getting away from the part you've passed and getting close the parts ahead? 
 A: As long as your speed is constant, there is no shift.
Imagine the sound you hear is because some portion of your emissions has radiated to the wall, reflected, then returned to you.  This path it took might be longer than the path it would take while you were stationary.
But the point here is that the path length it takes is constant.  As you move along the wall, there is no change in time.  That means the sound you hear is identical to the original sound, only delayed by a constant amount.  There is no change in pitch.
A: Let $f $ be the initial frequency $u $ be the speed of sound and $v$ be your speed (im assuming its constant)
So now the apparend frequency at the wall (say $f1$) can be expressed as follows;
\begin{eqnarray}
f1 = [u/(u-v)] × f
\end{eqnarray}
Then $f1$ is reflected back to you  so the frequency you hear(say $f2$);
\begin{eqnarray}
f2 = [(u+v)/u] × f1\\
f2 = [(u+v)/u] ×[u/(u-v)]×f\\
f2 = (u+v)/(u-v)×f
\end{eqnarray}
So as long as your speed is constant the frequency you hear will always be $f2 = (u+v)/(u-v)×f$ regardless to the distance between you and the wall
but if you are accelerating the $v $ increses every second so your apparend frequency will increase every second and vice versa when you decelarate.
Edit: Sorry i didnt consider "...parallel to a wall" ....my answer is valid when running towards a wall....when running parallel you take components of your velocity to the direction of the wall.since the sound you produced will travel in all directions you will get different apparend frequencies from different parts of the wall.so im not sure.but if you consider only the instance when you are perpendicular to the wall...the frequency you hear is always similar to the frequency emitted
