You need to use floor(random(1,4)
This will choose the number 1, 2 or 3 like you want. If you don't use floor then you will get back decimals like 1.2333452 which is why your Tone = 1 would never (well almost never) be true.
Also, you need to add the condition "Trigger once while true" to your audio triggers (and Start trigger as well, in your case), or else the audio will start to play a new instance every tick rather then just once.