Sound Test
From SmashWiki, the Super Smash Bros. wiki
Sound Test is an option that appears in all three Super Smash Bros. games.
In the first Super Smash Bros., one can unlock the Sound Test by completing Break the Targets and Board the Platforms with all 12 characters.
In Super Smash Bros. Melee, Sound Test is unlocked by unlocking all characters, stages, and beating every event match.
In Super Smash Bros. Brawl, the Sound Test is available without unlocking, probably due to individual songs being unlocked by finding CDs.
Sound Test allows the player to listen to all the music and sounds in the game. Players can listen to the voices of characters, stage music, and listen to other variety of sounds. Sound Test can be accessed through Option Mode.
