I do know one major difference between the sound from FM3 and FM4 is that FM4 has a dedicated LFE track to better support people with a Buttkicker. As far as I know this signal is routed through the subwoofer chanel. Maybe this causes the "hum". LFE signal tend to be loud and can drop below frequenties the average human can hear.
ITs probably the mangwang in your ear thats causing it.
I do know one major difference between the sound from FM3 and FM4 is that FM4 has a dedicated LFE track to better support people with a Buttkicker. As far as I know this signal is routed through the subwoofer chanel. Maybe this causes the "hum". LFE signal tend to be loud and can drop below frequenties the average human can hear.
Just my $0.02