Postby mmmason8967 » February 27th, 2015 6:35 pm
It's called a sokuon and is a small tsu. If you're familiar with hiragana, the katakana small tsu is used in exactly the same way as the hiragana one.
If you're not familiar with the hiragana small tsu, what it does is "double" the sound of the following consonant. For example, かこ is kako but かっこ is kakko. The pronuncation is actually a short pause--no sound at all. If you say "black cat" slowly, you say the "ck" at the end of "black" and the "c" at the start of "cat", but if you speed up and say it a normal talking speed, the "ck" at the end of "black" turns into a short pause--you say something like "bla' cat".
If the next character is し, the sound is a long "shh" rather than a pause. So in いらっしゃいませ, irasshaimase, the っしゃis pronounced like the double "sh" in "fish shop".
マイケル
