The part of a musical instrument that makes the sound louder.
A soundbox can make people think of music and fun.
Examples:
The guitar's soundbox makes the music loud.
I can hear the sound from the soundbox.
The soundbox is big and brown.
The cat is sitting on the soundbox and making it play music!
The soundbox is so big, it can make the whole room shake!
The soundbox is the best part of the guitar.