Emulator

Does disabling the frame limiter make the crackling occur sooner?
Does the crackling still occur if you make a save state, exit Dolphin and reload the save state?
Does this occur on all audio backends?

This happens in NSMB Wii HLE and other Games like DKCR as well, see issue 5938. Something seems to be severely broken on the audio side. All 3.0 revisions and 3.5 stable run fine.

Disabling the frame limiter does not make the crackling occur sooner. In my experience the crackling is more likely to occur after scenes that run slow, but I'm not 100% sure. Since it take a lot of time, the bug is very hard to reproduce in NSMB Wii.

However, in DKCR the cracking (HLE) sometimes occurs just after 5-10 minutes of gameplay.

I will try to answer Questions 2 and 3 using DKCR, but testing will take some time.

Can confirm this also happens in the Mario Superstar Baseball in HLE Audio on all backends. I have not tested LLE thoroughly enough.

Making a Savestate and reloading fixes the problem.

I have this issue in all games after a period of time (60mins+), reproduced with wii sports, wii sports resort, SMG, NSMB.

It occurred on all three backends on both HLE and LLE although I do more testing with LLE because I use that pretty much 100% of the time.

This issue does indeed occur in 3.5 and 3.0. See this thread for details:
http://forums.dolphin-emu.org/Thread-audio-glitch

After playing games like Zelda SS, SMG, Xenoblade and others for more than 200 hours with revisions between 3.0-424 and 3.0-750, I can be sure that the random noise did not occur in these revisions with HLE audio, at least not on my PC.

Dear all I've never heard any sound in any Dolphin version with out of the Wii Remote controlers or didn't you mean this?, not with HLE sounds, not with LLE ok but only lagging and hearing crackling noices.

Neither on AMD System Phenom II X4 955 with Gtx 560Ti nor with i5-3570k HD4000
Hope you can help me.

It's not about the Wii remote controllers, it's about a strange glitch in the audio back-end. Eventually, certain sounds (at least in my games) tend to get doubled or start crackling after playing a game for so long.

If you want Wii-Remote sound, you have to use LLE Audio(aside from some random sounds that do play in HLE), but due stuff about PCs, the audio on them tends to lag a bit. I don't know if there's a solution to that.

Thank you very much.

Could someone time the exact number of seconds before the crackling starts to occur and check if it's always the same?

It's not always the same Delroth; it can happen within a half hour, and sometimes take 3+ hours. (The game's I've seen it in have all used AX-HLE)

I can attest to that. I will say that on my machine, music with bass tend to make the crackling come and go the fastest (not sure if it is relevant though).

I've had the issue with Rune Factory Frontier (with HLE and LLE).
I haven't tested with the stable builds though.

It's the only game I've tried but I've found that the crackling will stop after a few minutes of gameplay (never the same amount of time before it stops, but it's less than the time it takes for the crackling to begin).

Based on haddockd1's comment on more bassy music, it sounds like it is a build-up of DC offset. In other words, the generated waveform signal is not always zeroed and eventually drifts away from zero somehow, either positively or negatively. You end up with clipping when the peaks of the signal pass by where they would normally be within range of the allowable bit depth, or perhaps the signal is flipping over from negative to positive (or vice versa) due to integer sign change causing major clipping artifacts.

I would venture to say that the issue is not localized to either HLE or LLE but is in code that deals with the audio pipeline after signal emulation occurs but before it is delivered to the audio driver.

The Audio glitch thread has had numerous folks confirm this issue on HLE and LLE, all backends.

I have had this issue occur on the latest build x64 3.5-1387 for the game:
Dokapon Kingdom. Should I write a new issue?

Why is this marked as "fixed" now? I am still experiencing this bug for sure.

because it was fixed in a1822a3acaf112dd37ed98818acdc0bc5014caba for lle and new-ax-hle

It was marked as fixed because it was thoroughly reviewed and fixed by ra1822a3acaf1 (3.5-1591) and a few tweaks up to r32579a08dd74 (3.5-1595). It has been thoroughly tested by tons of people, it's fixed. Update to that or newer and you will not experience the problem anymore.