Custom sounds not working

I am trying to implement a few custom sounds. The first one I made works fine. However, when I added the second one, it is not working. The first one still works the same, it is only the second one. Minecraft is still reading it as a sound with /playsound. Is there something I'm missing?
Here is my resourcepack/assets/minecraft/sounds.json file:
    "sound_a": {
    "category": "master",
    "sounds": [
    "sound_a"
  ],
    "subtitle": "subtitles.custom.sound_a"
  },
  
 "sound_b": {
  "category": "master",
  "sounds": [
  "directory/sound_b"
],
  "subtitle": "subtitles.custom.sound_b"
}
}```

Thank you for the help!