Matthew Gilchrest wrote:And I still think folks are missing the point.
First off, even if one can flap their lips slow enough, you need either 32' (for C) or 36' (for Bb) to get this note to actually resonate the "double pedal" inside of the horn. If one were to flap their lips slow enough, the tuba will resonate only the frequencies that agree with the amount of tubing they are traveling through.
If I flap my lips at 14.something Hz for a Bb, it's true that the instrument won't resonate at 14.something Hz. But the resonant overtones of 14.55 Hz. include 29.1, 43.7, 58, 73, 87, 102, 116, 131, 146, 160, and 175 Hz, through the 12th overtone. And the open bugle will resonaate at 29.1, 58.2, 87.3, 116, and 146 Hz out of that overtone series. It's true that not all overtones will resonate in a conical brass instrument (and it's a good thing, because if they did we would not like the sound). And it's also true that there may be alternate resonances that are not in the overtone series. If any of these fall on the overtones of 14.55 Hz that are not part of the 29.1 Hz overtone series, that it will create a 14.1 Hz difference tone.
Whether the effect of an infrasonic tone is produced will depend on whether that 14 Hz vibration can be felt (it won't be heard). But if any of the overtones produce that difference tone with enough energy, it might reach that point.
That's where the previous argument of being able to move enough air come into play. I agree that I doubt the physiology of humans sufficient to produce that much power, except possibly for a very short burst. How much power does it take to produce an infrasonic earthquake rumble in a theater that has Sensurround? The answer is LOTS. Humans just can't produce that kind of power for any length of time.
I have played a BBBb sub-contrabass tuba (if you can call it playing). I could hardly get it to resonate on any note, let alone its pedal. But that may have been a width problem as much as anything. That tuba (it's the instrument made famous by Hoffnung) is about the size of a small U-haul truck. I wonder if a six-valve Bb tuba would make that 14 Hz Bb overtone series possible, the same as I can play a 44 Hz F (which is the pedal on the open bugle of an F tuba) on the second partial with all six valves down. That theoretically makes it possible to play the 22 Hz double pedal F and benefit from a resonant instrument. I can't do it, but I'm sure better players can.
Another issue is the quality of the excitation. We develop a good tone as a result of sending pulses cleanly into the mouthpiece, creating a waveform that has the energy in it that will be transformed into a desirable sound after the filtering and amplification provided by the tuba. Playing the double-pedal by fluttering the tongue or by some other excitation method than a normal buzz would create a far different waveform.
In short, you may create a sound, and you might even get a hint of a 14 Hz vibration, if all the stars are aligned, for a short burst. But what people will hear are mostly the upper harmonics that happen to resonate in the instrument, plus whatever unresonant noise the instrument is unable to filter out. Fred Young called it a hammer on a frying pan.
Rick "recalling a Mythbusters episode in search of the 'Brown Note'" Denney
