Hello cousin Pedro - long time since we flew FB together mate! I'm glad to hear the CPL is going well
I didn't mean to suggest that the helmet would blot out the sound of the engine, far from it; more I was thinking that it would alter the ability to hear the various components and turn it into a continuous roaring sound.
I've just been reading pilot accounts of flying Hurricanes in the Battle of France and it's interesting to note the general comment on the sound of the gunfire when the button was pressed to unleash the 8 303's in the wings. All of them describe it a "crashing" sound, completely unlike the "taka taka taka" of popular fiction. Maybe it's because the latter is what gunfire sounds like from outside that it's often described that way.
Another popular comment was that sound also tied in very closely with what was being felt by the body due to vibrations through the airframe. One described "two bloody enormous explosions" behind him, combined with massive jolting sensations. He looked behind him, expecting to see that the back of the aircraft had disappeared, but it hadn't and he recovered and dived out to land across the Channel. Once down, inspection showed that the plane had taken two cannon hits only - one having hit a fuselage former and the other the armour plate behind his head! It's interesting to note that two cannon hits don't necessarily constitute a kill.
B