Virtually all turbofan engine blades exceed the speed of sound at high N1% even when moving slow (like during takeoff). This is part of what generates the disti

Virtually all turbofan engine blades exceed the speed of sound at high N1% even when moving slow (like during takeoff). This is part of what generates the distinct "buzzsaw" sound at or near max thrust when seated forward of the engines. The pitch/tone of the buzzsaw sound depends on the number of fan blades and rpm of the main fan (and likely stator design). In this video of an Iran Air 747SP the buzzsaw effect is particularly isolated/exaggerated due to the camera/mic placement, the use of 1970's design (louder) JT9D engines, and the shorter length of the 747SP. https://youtu.be/3lhHwKK-6ms https://youtu.be/3lhHwKK-6ms On a 737 the pitch is higher due to the smaller diameter fan (higher max RPM), while a 777 has the lowest buzzsaw pitch due to having the largest fan diameter. The most recent jet engines (like on the 747-8) have highly suppressed this sound with contoured fan blades.