What most distinguishes noise from music is the presence of

What most distinguishes noise from music is the presence of Regularity. Both of these relate to human power of hearing, the difference is that music is an arranged form of sounds which appeals to the aesthetic sense of human being while noise is a series of sounds with no regularity or harmony in it. Music and noise both have their good side as well as bad, with a common fact that any of them can be harmful for human ear when it is at a very loud frequency. 

mali had been a state inside of the ghanaian empire. after ghana fell because of invading forces and internal disputes, mali rose to greatness under the leadership of a legendary king named sundiata, the "lion king." the songhai empire, already weakened by internal political struggles, went into decline.

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there are isolated pockets of farming, generally around rivers and oases, which are used for irrigation.