O ACT Editor, there's a little feature on the right that is meant for adding sounds on a specific frame.
All you need to do is to add your own (that must be also patched on your wav/ folder on your GRF or data folder).
Click on the list and then on add new...
A pop-up will show asking for the WAV name, I like to add it with the file extension, just to be sure it will get the correct file:
After that, go on all frames (yes, it must be on the specific frame) you want to add the sound and select it on the list we previously discussed about.
Patch your sounds to your GRF/Data and test it InGame.
HINTS:
• Usually, the best way to make a sound fits with the animation is setting it to play on the frame prior the action, as an example, a footstep will sync better if it's set to play one frame prior to the foot reaches the ground.
• Sounds set on the first frames usually will not be played, go on the second or third frame of the animation to be sure.
• You can play multiple sounds on consecutive frames to mix their effects.
That's all, folks!!