There is no rule for that. You just have to learn the use of the apostrophe and s for each case. Don't be misled by your mother tongue.
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AnonymousWhy is it "Sound properties" and not "Sound's properties"?I can't answer why, but it's worth noting that if the first word references a person or higher animal, 1) we usually use the 's. Otherwise, the next most usual pattern is simply 2) two nouns in a row. The least used pattern is 3) the pattern with 'of', in which the head word is often