Posted by Gerald on December 05, 1998 at 15:51:28:
In Reply to: Re: Re: Re: Re: Re: Re: Re: false tones posted by Ken on December 05, 1998 at 10:13:44:
Actually I think the tuba played on the normal notes is acting as a n/2 wavelength. The vibrating lips alternately open and close the mouthpiece end. So it can act as double ends open half the time. That requires the length be any multiple of a half wavelength. The taper of the horn makes closing the small end less of an upset on the resonance. The pedal tones or false tones down below are using the horn in a quarter wave mode where the bell end is open and the mouthpiece end is closed half the time. That contributes to the rough tone quality.
While its been said that the tube ia halfwave long at the low Bb (on a Bb horn) and then the next open note is a octave above, that doesn't allow for the open F in between. That must then be a 3/4 wave resonance or else the fundamental of the horn is lower by half an ocatva than the lo Bb, but the first open note lower than that Bb generally is an Eb...
Its the details of the taper of the bore that makes the big difference between horns through out their register.