Silence is Golden

  I was recently reading a blog describing that persons manner of using  “Kiai” (“spirit yell”), as well as it's “use” in defensive applications. It was well written, but lacked in any actual application (information). It mainly focused upon the commonly held (and IMO, superficial) beliefs regarding it's use (while equally ignoring the weaknesses associated with it's use). The individual's stated reasons for it's use, consisted of the following:

When you wanting to channel/direct your energy.

 Hmmm, well this “breathing” thing is an internally controlled physical action. “Energy” (momentum??) is not controlled by breathing (except to a very minor extent). The implication (via this statement) is, that it is something else (I.E. “Chi”/”Ki”). Physical motion is how the directing of that momentum is accomplished, not through breathing. 

When you need to kickstart your fighting spirit (?).

“Spirit” is something one has, or doesn't, a breathing method will not change that. The implication is being made that one will “suddenly” become a better or more effective combatant via the act of “yelling”.

When you’re attacking or countering an opponent.

I agree with this statement, just not with the vocalized aspect of it (as explained later).

When you do a kata.

Again, I agree with the action, just not how it's commonly being done (vocalized).

When you want to demonstrate your power (?).

This one completely baffles me, why would I need to “demonstrate” power ?

When you need to breathe.

Vocalizing your breathing, is only informing your opponent “how/when” you will be breathing (an obvious weakness in one's defense). Ask any person who has done some (any) manor of “aerobic” exercises, the only thing that a student needs to learn, is to exhale (they will inhale, and do so without thought). It is very common for a person to “hold their breath” when beginning a confrontation. If they train to exhale with any/all motions that they perform, they will naturally inhale (thereby avoiding their own hyperventilation).

When you want to startle your opponent.

Though possibly providing some level of effect/response upon a completely clueless individual, an effectively applied technique is far more productive.

 These are all commonly believed and taught concepts. I just happen to not agree with how they are usually being taught.

Oyata taught us to utilize kiai, but he interpreted it more akin to how one should be breathing. As a combative component, it is more in accord with body motion/use (than as some extra/supplemental component).

 The body has natural reactions to certain actions when they occur, breathing is one of those actions. When the body inhales, internal organs (and body muscles) will relax. As the body exhales, those components will be inclined to tense (flex).

 This is clearly illustrated when numerous actions are being performed. (for example) When practicing the art of Shodo, the writer is taught to exhale in a smooth controlled breath. After initially inhaling, the body has relaxed (allowing the user to motion) and by then when exhaling in a smooth controlled breath, the user is able to (more effectively) control the actions of their brush. The same is true with the motions used in the performance of Te.

 In martial arts study, Students are taught to exhale during the performance of every performed physical action. This allows the user to maintain a level of control over when and how the utilized muscles are tensing while performing motions and remain relaxed when they aren't being used.

 Oyata emphasized the use of Silent (non-vocalized) Kiai. He didn't want students (vocally) “Kiai”-ing during the performance of kata, or at any other time for that matter. He viewed this as telegraphing one's breathing to your opponent. This would (in turn) inform them when it was most effective to deliver strikes upon you.

 I've recently (in the past 10 years or so) encountered students who are using a “hissing” instead of using (proper) Kiai breathing. Aside from sounding ridiculous, it is also incorrect (breathing). This “hissing” is only using air being exhaled from the (upper) lungs. A proper exhalation for Kiai, should come from the abdomen. This manner of hissing accomplishes nothing (productive). It additionally restricts the speed of exhalation (an important element of effective Kiai use).

 The (exaggerated) use of vocalized Kiai, is the equivalency to proclaiming to an opponent, when that opponent should strike the person (as well as informing them when their strikes are being delivered). 
 It could be argued that a vocalized Kiai could be considered the equivalent to calling out for help (though I doubt the effectiveness of that ploy). IMO it's more likely to alert an aggressors compatriots than to elicit any assistance from strangers.
 I've also heard it stated that there is an "intimidation" factor that presented with the use of a (loudly) vocalized Kiai. Personally, I find this to be one of the most ludicrous of the stated reasons. It reminds me of the "intimidation" argument presented by Police departments for their implementation of the PR-24 (side-handle baton). If someone isn't (already) "intimidated" by the firearm at your side, why would they be intimidated by a stick with a handle on it's side?
 The same is true with the use of Kiai, yelling loudly while attempting to hit someone else does nothing to intimidate the perpetrator of a crime (the aggressor). They expect someone to yell (to some extent). Yelling loudly (yourself) could be considered motivation for them, to shut you up (?). 

 Kiai can provide a conferrable advantage/improvement to one's technique application, as well as their defensive capabilities. The only (major) argument I would put forward (in regards to it's use), is that of providing excessive information to an opponent.  Therefore,  I am an advocate for Silent Kiai. I choose to avoid providing any more information to an aggressor than I have (no other choice) to.