deep voice; rich voice; full voice
Describes a voice that is low-pitched, resonant, and sonorous, often with a sense of strength or authority.
彼は太い声で話し始めた。
He began to speak in a deep voice.
その歌手は太い声でバラードを歌った。
The singer sang the ballad in a rich voice.
Compound of 太い (thick, deep) and 声 (voice). The phrase is transparent and follows standard adjective-noun modification.