Like light, sound can bend around the boundaries of an object it encounters as it travels through the air. 
This process is a function of frequency with higher frequencies (having wavelengths shorter than the size of the object) tending to be absorbed by or reflected off of the intervening object while lower frequencies (having wavelengths greater than the object) will diffract and bend around the object to continue their path at an attenuated intensity.

This leads to colouration of the perceived sound. 

This is an important issue in studio design and monitoring.