Some but not all martial artists will scream, and make other noises when fighting. Individual and teacher preferences influence these sounds. In some martial arts schools, each individual decides on the type of sound they will make.
Screams and vocalizations are not unique to traditional martial artists. Armies from ancient Greek times to today, make unique war cries, to great effect. Different examples of war cries and their impact.The vikings, when entering battle, brought trance-like warriors they called berserkers (“bear shirts”), who would show uncontrollable rage and make grunts and howls, as they indiscriminately attacked and killed anything in their path.
There are many reasons people make sounds when they fight. It affects emotional, psychological, and physiological states of the person making the sound and in others they are fighting. See Scientists Now Know Why People Scream. Screaming also occurs in the sports world. Why Do Athletes Scream?
A scream can contribute or take away from the power of a martial technique, depending on how the sound and technique are done. Some believe that it can also reduce injury, and reduce the risk that the yelling person will be knocked out if hit while yelling.
The principled coach or player might dismiss the importance of these things, and display their civility by refraining from yelling. The goal of a combatant should not be to be portray civility — the goal should be to awaken and manage one’s wild side.
Personality and individuality are important considerations. Some benefit from certain types of yelling, while others may not need to yell and still fight quite well. Sometimes, yelling will adversely affect the opponent, to the advantage of the person yelling. Sometimes, it won’t make a difference.
Those criticizing the use of yelling may be doing so because they do not understand why it matters, or they may not themselves benefit from yelling.
Proper yelling can help some fighters, while hindering their opponents. Stimulating your opponent’s senses with a properly timed yell can be an effective way to control or dull your opponent’s attention.