Play sound within limited region

Basically for my game I want to play sound say 5 units region. I have placed series of cannon at certain distance as per my game play. So I want to hear only nearest cannon fire sound and at present I am getting all tanks fire sound simultaneously.

I googled for this thing and at present I have this kind of inspector.

Please give me some suggestion for this.

You didn’t set your Spatial Blend to 3D.

If you set it to 2D, no distance settings are applied.

It will always be at the same volume in every channel.

Hi,
Have you tried playing sound using AudioSource.PlayClipAtPoint. You need to manage with in script when sound should play for each cannon.
This might solve your problem