Sound waves often bend around colunms in large concert halls. Is this a results of refraction or diffraction?

Like any wave, a (S ound wave) doesn't just stop when it reaches the end of the medium or when it encounters an obstacle in its path. Rather, a sound wave will undergo certain behaviors when it encounters the end of the medium or an obstacle. Possible behaviors include reflection off the obstacle, diffraction around the obstacle, and transmission into the obstacle or new medium. Basicly Diffraction.

This is the result of diffraction.