The Collaborative International Dictionary of English v.0.48:

Soundness \Sound"ness\, n.
   The quality or state of being sound; as, the soundness of
   timber, of fruit, of the teeth, etc.; the soundness of
   reasoning or argument; soundness of faith.
   [1913 Webster]

   Syn: Firmness; strength; solidity; healthiness; truth;
        rectitude.
        [1913 Webster]

WordNet (r) 3.0 (2006):

soundness
    n 1: a state or condition free from damage or decay [ant:
         unsoundness]
    2: the quality of being prudent and sensible [syn: wisdom,
       wiseness, soundness] [ant: unsoundness]
    3: the muscle tone of healthy tissue; "his muscular firmness"
       [syn: firmness, soundness] [ant: unsoundness]

The Free On-line Dictionary of Computing (19 January 2023):

soundness

   The quality of being sound (2).