Concerns' rhymes with:
concern's, concerns, concern's, concerns, concern's, concerns, concern's, concerns, discerns, adjourns, berns, burnes, burns, burns', byrne's, byrnes, churns, concern's, concerns, discerns, earns, ferns, hearns, kearns, kern's, kernes, kerns, learns, mearns, querns, returns, returns', sauternes, spurns, stearns, stern's, sterns, ternes, terns, turns, vernes, yearns
Concerns' sounds like:
censoring, coinsurance, concern's, concerning, concerns, concurrence, concurring, congruence, conjuring, conquering