During Tae Kwon Do practise we do yell at different occasions. This is called combatyell also. The Tae Kwon Do term for this yelling is Ki Hap.
The term Ki Hap consists of two parts Ki and Hap. Ki means energy (universal cosmos energy to be more specific) and Hap focus. Hence Ki Hap is a technique in order to focus the human energy. Therefore it is a concentration method.
The Ki Hap is capable of focussing and defocussing the energy in lightning speed. Defocussiong is neccessary for martial arts practioniers, in order to do additional movements fast. Ki Hap is the shortest possible concentration method.
The ability of rapid focussing and defocussion of energy promotes the Ki Hap method to an ideal method for martial arts practioniers.
The Ki Hap is executed via harnessing the Danjeon (two fingers below belly navel). The sound can sound differently, e.g long,strong and thick or short and thin.
The Ki Hap does end exactly with the supported technique, e.g. with the endmovement of a fistpunch.