Distinguished SOTW Member
Backus said thisI'm not sure what you mean in questioning how much vibration effect the reed movement could have on the standing wave.
The standing wave is vibrating air molecules, and the air molecules are vibrated by the reed movement.
As I was trying to say; (I believe) the mouthpiece creates and gives character to the standing wave by resisting and reflecting the vibration of the reed.
Any vibration of the mouthpiece would be the result of its failure to completely resist and/ or reflect the reeds vibration.
Less resistance to, and less efficient reflection of reed vibration on the part of the mouthpiece should mean more absorption and dampening of the reed vibration. Like a passive EQ, the sound may be shaped by attenuating certain frequencies; or like a compressor, the sound may be shaped by the cutting off or limiting a part of the attack of each note.
One theory is that any resulting vibration of the mouthpiece produces a sound that is loud enough to be detected.
Another theory is that vibration of the mouthpiece tip (like a second, or double reed) mechanically effects or works in conjunction with the vibration of the reed, and alters the character of the vibrational sound production.
My belief is that the vibrating mouthpiece does not produce an audible sound, but (if vibrating), absorbs and/ or fails to reflect some part of the reed vibration as it is setting the air molecules into motion, and as the vibration of the molecules reflects off the baffle.
It is probably important to separate in our minds, the purely mechanical vibration of the reed (like as you note the reed hitting the tip, which is initially mechanical), from the air molecule vibration which we sense as sound.
Reed vibration would produce no actual sound in the absence of air (as in the vacuum of space), but the mechanical vibrations would still be perceived like sound through the players physical contact with the mouthpiece and reed.
Did Backus actually say that the mouthpiece will not vibrate unless the reed hits the tip?
I know from my own experiments that with a large enough tip opening (or soft enough playing) the reed will not hit the mpc tip (confirmed by a dot of paint on the mpc tip not being picked up by the reed), yet the mpc still seems to vibrate.
Backus's further research reveals that the instrument's body vibrations are due to the reed vibrating against the mouthpiece, not due to the vibrations of the enclosed air column.
In a 1964 experiment, University of Southern California physicist Dr. John Backus attempted to determine the role of a clarinet's body vibrations in sound production.5 Backus's experiment centered on a clever and slightly comical gadget, with an artificial embouchure powered by a household vacuum cleaner. The clarinet's tone holes were all closed (simulating a clarinetist playing the instrument's lowest note), and the bell of the instrument was fitted with a muting device. When the clarinet was "played" via vacuum cleaner in this way, no sound waves could pass from the air column inside the clarinet directly into the air surrounding the instrument. Backus found that in this situation the instrument was virtually silent; the vibrating wood of the clarinet emitted such weak sound waves as to be inaudible to a human ear at a distance of one inch from the instrument's body. Backus concluded that the wall vibrations of a clarinet are too small to produce a perceptible sound. Further, he speculated that if it were possible to make the instrument vibrate sufficiently to be heard, the consequence would not likely be a pleasant one; he pointed out that a similar phenomenon occurs when one of the instrument's keys works loose and causes an annoying buzz. Backus's further research reveals that the instrument's body vibrations are due to the reed vibrating against the mouthpiece, not due to the vibrations of the enclosed air column.