If the distance between musicians is large enough, listeners may perceive waves to be out of phase. Typically, in this case, listeners perceive that one section of the band is playing their parts slightly after another section. This delay effect is informally referred to as ensemble tear or phasing (not to be confused with the music composition technique of the same name). Consider also that viewers perceive the movement of marchers as light waves. Since light travels faster than sound, viewers may perceive that movement is out of phase with the sound. Sound waves may also reflect off parts of the stadium or nearby buildings. For example, if two musicians, one standing on the front sideline of the football field and one on the back sideline, begin playing exactly when they see the beat of the conductor's baton or hand, the sound produced by the musician on the front sideline reaches listeners in the stands noticeably before the sound played by the back musician, and the musicians are seen to move before the sound reaches the stands. Ensemble tears can occur when musicians on the field listen to the pit. Because of the way sound waves travel, the sound pit produces first bounces off the back bleachers and then is heard by the ensemble. By the time the ensemble hears them, they are already late in timing. Because of this reason, the norm is to ignore the pit and let them listen to the ensemble for timing. Delay can be reduced in several ways, including: using compact formations; instructing players to watch field conductors, to get a uniform idea of tempo; instructing musicians to make constant adjustments and watch or listen to sources of tempo to make their sound reach the audience at the same time as other musicians; instructing players located near the back of the field watch the drum major, and all other players to listen back, playing along with those watching the drum major; instructing players to keep track of time and rhythm on their own (internalize the tempo); instructing the percussion to call out counts, or do rimshots (sometimes called cheaters) when they are not playing; instructing players to ignore the delay and realize that listeners hear the sound waves in phase. This most often occurs when the band is spread out, but in groups (e.g., the four corners of the football field in 4 groups).