A voiced plural is a plural formed by adding the plural -s suffix but with pronunciation changes; the final sound is voiced from a unvoiced consonant to an voiced consonant, and the plural -s suffix is pronounced /z/. This frequently happens to English words ending /f/ voicing to /v/, less commonly in those ending -th /θ/ voicing to /ð/ and with the word "house" /haʊs/ which ends /s/ voicing to "houses" /haʊzɪz/.
Ending in -f
e.g. dwarf-dwarves, elf-elves, hoof-hooves, loaf-loaves, etc
roof is generally pluralised as roofs, though this may be written rooves and pronounced /ru:vz/
Ending in -th
These are irregular in pronunciation only, as the English digraph th represents both /θ/ and /ð/ sounds.
e.g. truth, truths
Ending in -s
House - houses. the plural of spouse is spouses, pronounced //ˈspaʊ.sɪz/ (regular) /ˈspaʊ.zɪz/ (irregular-voiced). Note other words ending -ouse /aʊs/ tend to be either (1) irregular (e.g. mouse, louse) or (2) pronounced with /-z/ e.g. blouse