These effects can all be explained
because sound can be reflected just like light although of course sound is a longitudinal
wave.
It obeys the same laws of reflection but the amount of sound and light
reflected from different materials is different. The walls of rooms used to test sounds are
often covered with soft material or even projections like egg boxes to reduce the sound
reflection.
It is important to have enough sound reflection but not to much in concert
halls. Too little and the building is described as "dead" or "dry", too much and the echoes
from the walls interfere with the original music. The more people in a room the "deader" it will
be as regards the sound because the clothed human body does not reflect sound very
well.
You can investigate the laws of reflection of sound by the
following simple experiment.
Mount a piece of hardboard vertically and lay two
cardboard tubes on the bench in front of it. 10cm diameter tubes that have been used for
carpets are ideal. Put a clockwork watch or clockwork kitchen timer in one tube and put your
ear against the open end of the other tube. When the angles between the two tubes and the
hardboard are the same you should hear a loud ticking proving that the angle of incidence =
angle of reflection for sound.
