In order to more faithfully reproduce the correct inflection of a word, some signs were used for their phonetic values rather than their meanings. Eventually, Akkadians came to regularly use a group of signs for their phonetic values. We call these signs phonograms. Many of these signs are "simple" These signs became the Akkadian "syllabary.
Own work based on: http://www.ancientscripts.com/akkadian.html
Gire 3pich2005