I've got to agree with Bruce. Most people don't really kiai and I must include myself among them.
A real kiai is a separate attack. It will freeze a person. Ellis Amdur in his book Dueling with O-Sensei
tells of an incident where he used a kiai to stop his kid from running into traffic.
After practicing a few times, I start to lose my voice. I've heard of people who have ruptured the soft tissue in their throats and spit up blood after practicing too long. In his book Ki: A Road Anyone can Travel
William Reed recommends only 5-7 kiai during a practice session.
What does Iwama Ryu have to do with this? Are they suppose to always kiai during practice?