The goat horn play sound (not a specific type, just the generic horn sound probably added in a snapshot) and the goat horn breaking sound are sounds in the sounds.json that do not have files.

Here are some loading warns:

[17:41:32] [Render thread/WARN]: Missing sound for event: minecraft:item.goat_horn.play

[17:41:32] [Render thread/WARN]: Missing sound for event: minecraft:entity.goat.screaming.horn_break