Under this setting in the config file I use to set it as a C4 exploding. Now when I set it to that it won't make that sound. I've tried other sounds as well to no luck. Made the text bold so you can better see what I'm talking about. I tried Rockets, Stachels, Grenades, etc. No sound. I can get the Rocket to shoot up as a signal but yeah.
"Airdrop": {
"Default radius for location based massdrop": 50,
"Delay between Massdrop plane spawns": 0.66,
"Deploy Smoke on drop as it falls": true,
"Deploy with Audio Alarm on drop": false,
"Deploy with Audio Alarms on drop only during the night": false,
"Deploy with Spinning Siren Light on drop": true,
"Deploy with Spinning Siren Light on drop only during the night": false,
"Disable SupplySignal randomization": false,
"Massdrop default plane amount": 5,
"Multiplier for (plane height * highest point on Map); Default 1.0": 1.0,
"Multiplier for overall flight distance; lower means faster at map": 1.25,
"Prefab effect to use": "assets/prefabs/tools/c4/explosive.timed.deployed.prefab",
"signal rocket explosion timer": 15,
"signal rocket speed": 35,
"Use special effect at reaching ground position": true
},