‘Hoarse’ means a ‘rough or raspy’ sound.  A person who has a hoarse voice sounds like they cannot talk much louder than a whisper.  The words hoarse and horse are homonyms.

[我想他應該感冒了，他的聲音聽起來有點沙啞。]

本句取hoarse與horse相近音，形容人因為感冒而聲音有點沙啞，而不是真的變成一匹小馬喔!