In Japanese, there are some sound differences that clearly distinguish words from one another, such as falling on a different 行 or 段 on the 五十音 ([傘]{かさ} vs. [風]{かぜ} or [友]{とも} vs その); while other sound differences make no difference as all (English 'l' vs. English 'r', vanishing <u>
sounds, ヱビス vs. エビス).
Where on this spectrum does voicedness (e.g. さ vs. ざ) fall?
(I am aware that words are spelled one way or the other, but then you get situations like [出島]{でじま} vs. [広島]{ひろしま} where the 島 is clearly the same word, or the somewhat more extreme [仲田]{なかた} vs [仲田]{なかだ}.)