Diffraction

As sound waves meet an opening in a wall, they spread out in all directions making a spherical pattern, provided the opening is smaller than the wavelength. This opening can be seen as a new sound source. If the opening is larger than the wavelength, on the other hand, the sound waves spread out uniformly. The effects of diffraction can, however, be observed at every kind of corner. Low-frequency waves are more subject to diffraction than higher-frequency ones.