The sound issues only happen when the emulation-speed gets below 100%. That happens because this is probably the most demanding game for Dolphin and your CPU is too week. Clocks below 3 GHz are just too little. If you have room for overclocking, that might help a bit.
Intel i5-4690k (Devil's Canyon) @ 3.5 GHz (+Scythe Mugen) / Gainward GTX 1070 Phoenix (OC'd) / ASUS Z97 PRO GAMER / 16GB G.Skill DDR3-2400 CL10 TridentX / X-Fi XtremeMusic / Win10 Pro 64bit / Dell S2716DG Monitor / 3x original WiiMote+MotionPlus+Nunchuk
