In Windows, try going to:
Control Panel > Sound > Speakers > Properties > Enhancements and disable all enhancements. Click Settings and disable Boost level.
Also in the Speaker Properties, go to the Advanced tab and enable "Allow Applications to take exclusive control of this device" and "Give exclusive mode applications priority".
One other thing is to try an old version of Dolphin and use 32000hz (instead of 48000hz) in the DSP settings.
Control Panel > Sound > Speakers > Properties > Enhancements and disable all enhancements. Click Settings and disable Boost level.
Also in the Speaker Properties, go to the Advanced tab and enable "Allow Applications to take exclusive control of this device" and "Give exclusive mode applications priority".
One other thing is to try an old version of Dolphin and use 32000hz (instead of 48000hz) in the DSP settings.