Your
sounds.json
and registering code looks correct as they are here.
My experience is that when you try to play a sound using the SoundEvent object returned from the registering method, it just doesn't work. I had to retrieve the SoundEvent directly from the registry using something like this (adapted for your mod):
playSound(entityName, entityName.getPosition(), SoundEvent.soundEventRegistry.getObject(new ResourceLocation(ModReference.modid, "entity.terrakon.bark")), SoundCategory.NEUTRAL, 1.0F, 1.0F);
Edit: Well nevermind then, I'm glad you got it working. I unfortunately have no clue how to implement sound subtitles as of yet.