IPA: /ˈsaʊndbɒks/
KK: /ˈsaʊndˌbɑks/
A hollow part of a musical instrument that helps produce sound by resonating.
The violin's soundbox amplifies the music played on it.
Soundbox → The word is formed from "sound" (from Old English *sund*, meaning noise or auditory sensation) and "box" (from Old English *box*, meaning a container). A soundbox is essentially a container that produces or holds sound.
Think of a 'box' that holds 'sound' — that's what a soundbox is, a container for sound.