I read it.
Sounds... Well, not sounds, but reads just like harvesters dumping tiberium in refineries to me. When you have big spending and several harvesters doing their little spurts in their refineries, sometimes the frequencies get high. Unlike in RA, where ore trucks just dump everything on the floor in a second flat, in TD harvesters deposit tiberium in little portions over a larger period of time. When these sounds interlace it sometimes resembles what you're describing. But we can't really hear what you hear, do we? Now, if the 'muffling' and 'crackling' also happen when you're JUST spending, or JUST processing credits, you may have a technical issue. If this is the case, it helps to be more specific, like post your system specifications, so some of the people on this board who know about computers (not one of them) can help you. The last thing I can think of is: are you talking about multiplayer games or single? Because lag too can cause the credits sfx to glitch.
Well, I apologise for that oversight, I was a bit vague. I am running Windows 7, I use a USB headset, the drivers are up to date, as in the original post the game is fully patched. I just tested it ingame again, first test was with 1 harvester and a refinery, sound spikes as expected, the next test I used 3 refineries and 3 hervesters, all unloading at the same time, no difference in the frequency of the sound spikes. From what I heard there was no increase in the intensity of the sound spikes between the two tests. These tests were carried out in single player, and also network play with AI players. I have not tested it online with a human player.
I'm going to use this persons gameplay video to try and share what it sounds like, not sure if you can embed videos on here so I will link it to a specific point. (skip to 7mins 10secs) Command & Conquer: Tiberian Dawn "Walkthrough" [Nod] Missions 1-3
I know this is such a trivial problem, and I probably shouldn't have bothered with this thread but I thought I might as well share it just to see if anyone else has experienced this too.
I apologise if it is hard to make out, I would have recorded a video myself without any music or gunfire but i'm not very good with recording; but at this point in the video onwards where he trains a minigunner, builds a structure or gathers tiberium it is quite a distinct sound.