What does "sound engineering" mean in this context: "Establishment and use of sound engineering principles to obtain economically software that is reliable and works on real machines efficiently. (Fritz Bauer)"?
The definition above is for software engineering. However, the word "sound" used here definitely is not engineering for audio.
The first definition of sound in most dictionaries has to do with something auditory, from the Middle English soun or Old French son. The second involves things that are free from defect or healthy, from the OE gesund. (Ref: The Free Dictionary).
The writer is referring to the latter, namely engineering practices that are free from defect, trustworthy, marked by good judgement, or compatible with an accepted point of view (definitions 1, 9, 10, and 11).
Ah, here we have sound as an adjective, modifying engineering principles. In this sense, usually considered its second sense, sound means something like strong, secure, or reliable; or competent; or in good condition.
So it is engineering principles that are reliable and safe, probably.
Sound:
: solid, firm; also : stable
The definition above is for software engineering. However, the word "sound" used here definitely is not engineering for audio.So we're after some other non-audio definition of sound that can be looked up in a dictionary. And the three given answers are pretty much general reference answers.