Sound and Syllables 「Cont.」
Double consonants in the Japanese language is interesting, they work similarly to double vowels insofar that you add a second one to the primary consonant. Other than that similarity, they are functionally different, the first way in which they differ is that the second consonant will always be the same as the the primary, also, there is no shorthand indicator that there is a double consonant unlike that with a vowel.
Double vowel word
Double consonant word
However, the biggest difference between a double consonant and vowel is what is done in the case of pronunciation of the word in Japanese. While, as previously stated a vowels' sound is extended「not altered」when doubled, a double consonant is slightly different in approach. When a double consonant is present in a Japanese word, there is a slight pause in the annunciation of that part of the word that has the doubled consonant. So in the case of a single consonant word such as sekai 「世界・World」it is simply pronounced as you see each sound [Seh-Kah-Ee] but with the consonant doubled like in the above example of Sekkei「設計・Design」it is pronounced [Seh-k--kei] there is about half a second of holding onto the beginning of the sound of the consonant. Other than that double consonants are easy to learn with practice, and keeping your eye out for them in words you are unfamiliar with, for there are similar words in Japanese where one word has the double consonant and the other does not, this can of course deliver the wrong message when speaking, but as long as you remain observant you shouldn't have any issues.
Language is something that should be enjoyed, have fun!
〈( ^.^)ノ Koyuuki (*^｡^*)