Why is–[ul]
[li]Volume–the ammount held inside a container the same as–[/li][li]Volume–the loudness of a noise the same as–[/li][li]Volume–a book on a shelf, in a series of books?[/li][/ul] 
Same basic reason that you set a tea set by the TV set. Other than that, I guess we just have to reuse some words to keep from having to make up new ones.
“Volume” appears to have been derived from a French word meaning “to roll” and was used to describe “rolls of parchments” for example.
From there, the use of “volume” to describe a roll of parchments expanded to include books, which was the successor to parchment rolls.
From there, it apparently became used to describe “large amounts” as early as the 1600s, possibly because books (volumes) contained large amounts of sheets, and later it meant “amounts” in general, regardless of size.
“Volume” as a reference to sound amplitude is probably just an extension of its meaning of “amounts.”
Volume is from the Latin volumen, “scroll.” The original meaning in English appears to have been what it is now in the world of academic journals: a series of issues of a periodical, or a series of printed sheets bound into a book. If you think of each printed sheet in a book as a separate document, the essence of the word “voluminous” becomes clear. From that, hold onto the concept of “lots of it,” because by the 16th century, the adjective “volume” had come to refer to a large amount, and thence to the scientific concept of measuring cubic capacity. I expect the concept of audio volume (filling a room) proceeds directly from there.
Grr! Curse your fast typing!
That reminds me. I have to dash out the garage, and dash off a quick postcard on the dashboard of my truck.
Dash it all!
If a man harvests wheat with a buggy whip, does he crop his crop with his crop? 