Pedal Tones (Physics Perspective)???

[NCSUSousa]

You are confusing wave length of pitches with the length required to produce and enforce said pitch. They are not the same.

I suppose I might be confusing some of the terms here. Since you're an expert, why not enlighten us?

Tomorrow I'll arrange with the guys in the shop to make a video (three tuba players in the company). We'll connect a reed motor to a tuba and show you all that the tuba will resonate and make a clear, discernable tone no matter what valve combinations are pushed, nor what pitch is fed into the tuba.

I will definitely look forward to this video.

Again, the tuba is only a resonator and as such things like; 'open tube, closed tube, partially open tube' mean nothing here. I'll say this again, the resonator will resonate with whatever pitch you put into it.

I can agree about quitting calling it a closed, open or otherwise. Brass instruments are just too complex to try and equate directly to one of the simple physical models.
Fortunately, scientists have already mapped the impedance of instruments such as the trumpet and trombone. The point I've made here in referencing the science research is this - some pitches will resonate BETTER in a given length of pipe. That's how most of us play tuba. We stick to the lengths of pipe (by use of valves) that resonate BETTER for the note we're trying to play.

The fundamental pitch for an 9' (open as that is what ALL resonators are) pipe is AAA#, or 'Pedal' Bb for a trombone, two spaces below the bass clef staff.

I've already pointed out that a ~9' trombone shaped pipe will resonate on Bb1. That's the accepted 'pedal' tone for a trombone. According to the physics research I've referenced, the trombone isn't resonating optimally at that lowest frequency, but it doesn't really matter if it's optimal at that frequency because the overtones resonate quite well and we still perceive the 'pedal Bb' sound.
Also according to the simplified physics equations, that Bb1 isn't the fundamental frequency for a 9' stick of 3/4" plumbing pipe. It may also be the frequency used in an organ pipe, but again - I'm not playing an organ pipe (or a piece of simple copper plumbing pipe), I'm playing a tuba. I'll stick with what works for a brass instrument player.

You are all also seemingly forgetting that we almost universally work in the harmonic series ABOVE the fundamental length of the brass instrument we are playing. So for there to be any sort of claim that when we play a 'Pedal' note that the instrument isn't resonating and that we are only hearing harmonics is completely false.

Actually, I linked to Rick's page on this subject in my very 1st post. There are many others (the hyperphysics page link for example in the most recent post) that also point out that the higher harmonics are present and amplified. That's what links are for - so we don't have to re-type something that someone else has already done well.

[timothy42b]

So for there to be any sort of claim that when we play a 'Pedal' note that the instrument isn't resonating and that we are only hearing harmonics is completely false.
.

Probably not completely false.

Actual measurements on pedal tones show little or no fundamental content.
Experiments feeding the ear a tone composed of overtones with no fundamental content at all show the ear will perceive the pitch to be that fundamental, if the overtones are in the series that would be expected.

Tomorrow I'll arrange with the guys in the shop to make a video (three tuba players in the company). We'll connect a reed motor to a tuba and show you all that the tuba will resonate and make a clear, discernable tone no matter what valve combinations are pushed, nor what pitch is fed into the tuba

Any system will vibrate at any input frequency, but if it's far from a resonance it won't vibrate very much.
I don't know what a reed motor is, but unless it outputs a pure sine wave you haven't proved your case. If the waveform is at all complex, then the higher overtones may very well be exciting the horn. (and if it sounds like a buzz, it's got some square wave content and a huge amount of odd number harmonics)

[bud]

Bump

[Erik_Sweden]

Where is the reed-motor-to-a-tuba video ?

[Erik_Sweden]

Where is the reed-motor-to-a-tuba video ?

Lost with the former employee that made it I suspect.
I recall making it, not much else. I'll try to replicate next week in the shop.

Nice. Thanks

[MaryAnn]

I didn't read the entire string but hope someone noted that a tuba is not cylindrical, and that conical harmonic series will not be the same. You may find the below of use in some way; written by a high level horn playing professor of physics who used to have a lecture in which he put all the parts of a trumpet together, one by one, starting with a cylindrical tube, and showed how adding things like the lead pipe, the bell, and the mouthpiece created the harmonic series we are familiar with. His name is Brian Holmes.
https://www.dropbox.com/sh/t35dsgo1dgmm ... uments.pdf" target="_blank

[DonShirer]

This topic is so old I had to read it again to remember what was said, but several posters did point out the series differences you mention, MaryAnn. Of course a tuba is more complicated than a simple cylindrical or conical resonator. The Holmes (trumpet-playing physicist) article has some good stuff, not much directly appropo to pedal tones, but he does get kudos for citing Art Benade. Thanks for the link!

Don (tuba-playing physicist) Shirer

[GC]

But the whole matter of "false tones" arises when the produced tones DON'T match the resonant pitch or harmonic series, and many of us can play them. It's still of major interest why some horns respond so well to them and so many don't.