Let’s start this article with the definition of standing waves: what they are and how they impact your listening experience. Standing waves are areas of high and low pressure within your room. A room is a box. It can only hold so much pressure. Up to a certain level it is fine. After that point, based on its size and volume, it will tell you how much and at what frequency it’s not happy. It expresses this discontent through room modes: areas of high and low pressure for frequencies below 300 Hz.
Think of a weather map on television and you’ll see that you have areas of low and high pressure. This is atmospheric pressure but it’s pretty much the same concept when it comes to your room. In your room, it’s sound pressure. If you mapped the areas of pressure in your room, it would look much like that weather map, with areas of high and low pressure are distributed throughout the room. They do not move clockwise and counterclockwise like atmospheric pressure, but they do exist between two or four room boundary surfaces and can be 3 to 4 feet in width. Their amplitude, their strength, depends on the degree to which low frequencies do not fit into the room.
Full story Via audiophilereview.com