Acoustical shadows or quiet regions can be produced when there are long overhanging balconies or other structures jutting into the hall. There should be a large open space extending over a large angle in front of each person in the audience. When any observers's view is blocked or partially blocked by some protruding object, such as a balcony, wall or column, the sound will undergo diffraction around the structure. As we have seen, the diffraction is different for different frequencies, leading to distortion of the sound passing by or around the obstruction.