Koopmann rhymes with:
coopman, koopman, coopman, groopman, koopman, shoopman, chapman, chipman, clapman, coopman, copeman, groopman, hapeman, hopman, kampman, kampmann, koopman, krupman, lampman, lipman, lippman, lippmann, lopeman, midshipman, shipman, shoopman
Koopmann sounds like:
kabbani, kaboom, kapaun, kasabian, kassebaum, kauffman, kauffmann, kaufman, kaufmann, kavan, kaveney, kayvon, keaveney, keaveny, kevan, keven, kevin, kievan, koeppen, koffman, koopman, koppen, koven, kuban, kubena, kubin, kuvin, kvam, kvamme