Our dictionary defines the word obscure as not clear or distinct, not easily understood and then gives an example of an “obscure figure in the fog”.
Here are some great examples from Youtube. I found two old recordings from famous people. Their voices are obscured when compared to our modern technologically advanced recordings.
An obscured reading of the poem America by its author, Walt Whitman from 1890:

Thomas Edison used a wax cylinder to make a recording to business associates.

This recording is even more obscured than when first recorded because it got moldy. Thomas Edison’s voice is faint in the background.