in 737 i use a fitted ear piece that was molded to my ear back in DEN (very common in the states and i think would make for a good business adventure here in europe) for the left ear that is attached to the headset. and an ear plug in the right ear. (sitting in left seat). the ear plug cuts all the trash noise out and i do not have much problem at all with hearing FO's or even the cabin crew who says its too cold.
i was in twin otter for too long and then C130 too long and had to use Dave Clarkes and ear plugs under that to survive.
and i do climb and descend at 280 knots not only for sound but for unexpected turblulence that i have encountered more than once and it makes a good transition to the cruise speed. some FMC's you have to watch but most flow easily from 280 to the mach cruise. and the QRH performance is usually 250/280/.74 anyway so i use that to reduce the variables. and when turbulence hits in climb or descent, i don't have to change speed.