Ƙofar rage hayaniya gabaɗaya ana yin su ne daga ƙaƙƙarfan abubuwa masu tauri.Waɗannan ƙaƙƙarfan abubuwa masu kauri kuma suna aiki da kyau wajen nuna sautin baya ga tushen sa.
Ƙarfin ƙofa don rage amo ana kiranta tasirinta na watsa sauti (TL).Mafi girman TL, mafi kyawun sakamako.
Ƙimar watsa sauti (STC) tana magance wannan matsala ta hanyar ba da ƙima ɗaya ga aikin sauti na kofa.Mafi girman ƙimar STC, mafi kyawun ƙimar kuma mafi kyawun aikin.