I do have the follwing error when starting my Mod Client:

 

Spoiler

[19:49:36] [Forge Version Check/INFO] [ForgeVersionCheck]: [forge] Found status: OUTDATED Target: 13.20.0.2296
[19:49:39] [Client thread/WARN]: File minecraft:sounds/p99/shot.ogg does not exist, cannot add it to event survivethis:p99_shot
[19:49:39] [Client thread/WARN]: File minecraft:sounds/p99/reload.ogg does not exist, cannot add it to event survivethis:p99_reload
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby01.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby02.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby03.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby04.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby05.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby06.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby07.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby08.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Client thread/WARN]: File minecraft:sounds/bullet/flyby09.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:39] [Sound Library Loader/INFO]: Starting up SoundSystem...
[19:49:39] [Thread-8/INFO]: Initializing LWJGL OpenAL
[19:49:39] [Thread-8/INFO]: (The LWJGL binding of OpenAL.  For more information, see http://www.lwjgl.org)
[19:49:39] [Thread-8/INFO]: OpenAL initialized.
[19:49:39] [Sound Library Loader/INFO]: Sound engine started
[19:49:44] [Client thread/INFO] [FML]: Max texture size: 16384
[19:49:44] [Client thread/INFO]: Created: 16x16 textures-atlas
[19:49:45] [Client thread/INFO] [FML]: Injecting itemstacks
[19:49:45] [Client thread/INFO] [FML]: Itemstack injection complete
[19:49:45] [Client thread/INFO] [FML]: Forge Mod Loader has successfully loaded 5 mods
[19:49:45] [Client thread/INFO]: Reloading ResourceManager: Default, FMLFileResourcePack:Forge Mod Loader, FMLFileResourcePack:Minecraft Forge, FMLFileResourcePack:Survival Mod...
[19:49:47] [Client thread/WARN]: File minecraft:sounds/p99/shot.ogg does not exist, cannot add it to event survivethis:p99_shot
[19:49:47] [Client thread/WARN]: File minecraft:sounds/p99/reload.ogg does not exist, cannot add it to event survivethis:p99_reload
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby01.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby02.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby03.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby04.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby05.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby06.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby07.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby08.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/WARN]: File minecraft:sounds/bullet/flyby09.ogg does not exist, cannot add it to event survivethis:bullet_flyby
[19:49:47] [Client thread/INFO]: SoundSystem shutting down...

 

So I checked my: sounds.json and it looks like

 

{
  "p99_shot": {
    "category" : "player",
    "sounds": [{
        "name": "p99/shot",
        "stream": false
      }
    ]
  },
  "p99_reload": {
    "category" : "player",
    "sounds": [{
        "name": "p99/reload",
        "stream": false
      }
    ]
  },
  "bullet_flyby": {
    "category" : "player",
    "sounds": [
      {
        "name": "bullet/flyby01",
        "stream": false
      }, {
        "name": "bullet/flyby02",
        "stream": false
      }, {
        "name": "bullet/flyby03",
        "stream": false
      }, {
        "name": "bullet/flyby04",
        "stream": false
      }, {
        "name": "bullet/flyby05",
        "stream": false
      }, {
        "name": "bullet/flyby06",
        "stream": false
      }, {
        "name": "bullet/flyby07",
        "stream": false
      }, {
        "name": "bullet/flyby08",
        "stream": false
      }, {
        "name": "bullet/flyby09",
        "stream": false
      }
    ]
  }
}

 

 

My files are all there, in the directory:

 

C:\Modding\mod1\src\main\resources\assets\survivethis\sounds\p99\

C:\Modding\mod1\src\main\resources\assets\survivethis\sounds\bullet\

 

containing all the files of type "*.ogg"

What did I miss?

The name property of your sounds is a resourcelocation and must include your modid. Currently it has none and the game assumes they will be located withing minecraft's assets.

FYI - sounds are non-streaming by default so you could take some shortcuts in your definition:

"bullet_flyby": {
    "category" : "player",
    "sounds": [
        "modid:bullet/flyby01",
        "modid:bullet/flyby02",
        "modid:bullet/flyby03",
        "modid:bullet/flyby04",
        "modid:bullet/flyby05",
        "modid:bullet/flyby06",
        "modid:bullet/flyby07",
        "modid:bullet/flyby08",
        "modid:bullet/flyby09"
    ]