djm, I do not know if the grooves would increase the airspeed and by that the loudness. I just thought that aerodynamics at the far edge and the outside of the embochure hole are important. An increase through an overcut (like Glauber’s pic shows) and the resulting sharper edge may be just as important. Maybe one or several grooves are a compromise to add some area of increased sharpness while leaving some normal, which may be better for response in different octaves. But I have no idea there, I am speculating.
I also do not imagine pressure waves travelling up and down the flute, being reflected at the toneholes. I imagine the whole column vibrating, going from a high pressure (expansion of all the air) to a low pressure (compression) and back. The air expands and leaves the tube at both ends simultaneously, and contracts and enters the tube at both ends simultaneously, back and forward at the frequency of the tone produced. The energy of this vibrating air column would be proportional to the amplitude of the vibration and its frequency.
The magic of the flute is that it is just this vibrating air column which pushes the surrounding air into vibration, so we can hear the tone. Nothing physically solid needs to vibrate, no reed, no string, no goat skin Pure vibrating emptiness!
hans, i think you’re right. i just did the HJ test. virtually no air coming out the end. i had always operated on the assumption that at least some air in part actually got directed into the hole to create some turbulence within; and that maybe “undercutting” of the blowhole helped defined this interaction. are you saying no air gets in the hole, passing the imaginary surface line of the hole? very interesting stuff.
Very little. The air that hits the edge alternates rapidly between flowing inside and outside, and this is what causes the sound. The majority of the air is wasted and this is why a trumpet uses a lot less air and sounds a lot louder than a flute.
Air does go in and out the embochure hole and the vent hole, but it does not stream in nor stream out like the breath. It gets pushed in and out through the expansion/contraction cycles of the vibrating air. That is why large holed flutes with larger embochure hole can play a bit louder, the holes alow a better movement for the vibrating (sounding) column of air. Even better on the Boehm flute. Smooth edges of the holes help this movement too and prevent excessive turbulence, which means a cleaner tone. So if there would be an imaginery skin with no resistance at the entrance to the embochure hole it would vibrate like a drum skin, well, like an ideal drum skin without rim, like a piston. So a little air goes always backwards and forwards, and I imagine we play with this trying to achieve certain tone characteristics.
Pure vibrating emptiness!