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Thread: ' over blowing '

  1. #1
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    \' over blowing \'

    When you 'overblow' a pipe ....
    What's the first note that happens?
    In relation to the 'unoverblown'
    note ???
    Same would apply to a flute and
    perhaps even a bugle ?

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    Captain of Water Music Thomas Dressler's Avatar
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    Re: \' over blowing \'

    That's a good question--I believe pipes will overblow according to the harmonic series, which would mean the first note to overblow would be two octaves above the fundamental (the "unoverblown" note.) I can't state this as an absolute fact because I'm not a builder. Perhaps someone can give us a physics lesson?

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    Re: \' over blowing \'

    >That's a good question--I believe pipes will overblow >according to the harmonic series, which would mean the first >note to overblow would be two octaves above the fundamental
    >(the "unoverblown" note.) I can't state this as an absolute >fact because I'm not a builder. Perhaps someone can give us a >physics lesson?

    Isn't the 'harmonic series' simply 1,2,3,4,5,6,7
    I.E. If overblowness proceeds by this series, then
    the first overblownote would be 2*fundamental
    One octave above the fundamental
    Actually though I think it may do some sort of cycle
    of fifths....?????????????

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    Captain of Water Music Thomas Dressler's Avatar
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    Re: \' over blowing \'

    Yes, you're right about the first one being one octave higher. I'm not sure what I was thinking! The first one is an octave higher, the next one is a fifth above that, the next one is TWO octaves higher, the next one is a THIRD above that, then the fifth, then a "blues" note. . .the thing is that the notes in the overtone series get closer and closer together as they go up (and less and less equal tempered.)

    And I think organ pipes will overblow through the harmonic series, just like open brass instruments will. But I can't say that for sure.

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    Re: \' over blowing \'

    Try this one - http://en.wikipedia.org/wiki/Harmoni...es_%28music%29 - it should explain it to you.

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    Re: \' over blowing \'

    Yea. Thank you both. I found another good link (below)
    Nobody seems to use the term 'overblow' though. But this
    term is used with pipe organs...Right ????
    http://www.phys.unsw.edu.au/music/basics.html

  7. #7
    Captain of Water Music Thomas Dressler's Avatar
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    Re: \' over blowing \'

    Yes, at least here that's the word we use. I seem to recall that word used many years ago when I was learning to play the recorder, too. I'm thinking about this. . .I believe when it comes to reed pipes you don't hear the word "overblow" so much as you hear people say it "flies off pitch." That's probably because with reed pipes it can be as much a problem with the reed as it can be with too much wind. Of course, a flue pipe will "fly off pitch" too if you mess with the lip. Wish we could get an organbuilder to come into this discussion!

    Thomas Dressler

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    Re: \' over blowing \'

    Of course, a flue pipe will "fly off pitch" too if you mess with the lip.
    I'm trying to investigate where the pipe itself switches 'modes'(term?) ..... Assuming constant
    'lipness' ............ mike

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    Captain of Water Music Thomas Dressler's Avatar
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    Re: \' over blowing \'

    Do you mean you want to know how much to increase the wind pressure to cause the pipe to overblow, without adjusting the voicing of the pipe (the lips?) That I could not answer, but I'll say that I would think it would depend on a couple things. Pipes are voiced for specific wind pressure. The amount of air entering the pipe is controlled by opening or closing the toe hole, and the sheet of air aimed at the upper lip to cause vibration is adjusted with the lower lip and the tongue (or languid.) I would think the amount of air needed to cause overblowing would vary depending on how the pipe is voiced.

    Also, there are pipes called "harmonic" (mostly flutes) that have a hole in them, causing the pipe to speak at a harmonic, with less harmonic development in the actual sound because overtones are less developed. (I believe that's the theory.)

    Does this answer your question at all?

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    Re: \' over blowing \'

    http://www.quarter-wave.com/

    >Does this answer your question at all?

    Somewhat I'm sorta in over my head.
    I hope I'm not too OT but here goes...
    (see above link)
    There is a type of speaker enclosure
    known as a TL (transmission line).
    In essence it is a closed (1/4 wave)
    pipe with (rather than a 'lip') a 'driver'
    (what we would normally call a 'speaker'
    (the thing with a cone and a magnet)) on the
    end. One characteristic of this configuration
    is that there is little bass without a certain
    volume. I'm trying to figure out what's going
    on.
    Your referance to 'pressure' may be the clue.
    Is it possible for a pipe to be 'underblown'?
    I.E. without sufficient pressure does the pipe
    fail to voice at all? And I don't mean just be
    too soft in output. I mean fail to develope a
    discernable fundamental......Thanks for the
    input............mike

  11. #11
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    Re: \' over blowing \'

    The overblowing for normal open pipes is the same as it is for most all woodwind and brass instruments, namely, (starting from the main note)

    In this case we'll speak of a pipe playing "C"

    Jumps an octave (from the main note, to it's octave ), then a fifth, then a fourth (to the second octave), then a MAJOR third (to the Tierce pitch), then another major third (to the Quinte pitch), THEN a MINOR third (To the famed Septieme), then a Major Second (playing it's third octave), then another major second (playing D), then E, F, G, A, Bb, B, then C, then C#, D, D#, E, F, F#, G, G#, A, A#, B, C........ Etc. continuing in the same fashion......

    And it just keeps going up from there.....

    To get a pipe to overblow requires opening up the toe hole's diameter, and making the windstream slightly thinner and more focused by closing the flue up very slightly, pushing it more towards the languid. You could leave the flue intact as is, but it would require a larger opening thus further, and it would be considerably louder as well.

    Julien A. Laurent

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    Captain of Water Music Thomas Dressler's Avatar
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    Re: \' over blowing \'

    Well, I took a look at the link you gave, and without spending a lot of time on it (I can't right at the moment) I wasn't able to ferret out the basic workings of this speaker.

    But to answer your question, yes, if the pressure is low enough the pipe either won't speak at all or will make some off pitch weird sounds.

    But I think we're talking about two different things here. I'm thinking your speaker probably works more like a reed pipe, where the pipe itself functions only as a resonator. The sound of a reed pipe is made by a vibrating metal tongue, or reed. In the case of your speaker, I believe the sound comes from a vibration caused by an electromagnet, and then the enclosure, or the "pipe" acts as a resonator. In this case, wind pressure would not really be of significance, I believe, because it would be the intensity of the vibrations from the electromagnet that would increase or decrease volume.

    In the case of a flue pipe, the sound is created in a very different way. A flat sheet of air is aimed at the upper lip of a pipe in a way that causes it to be unstable. It can't decide which side of the lip it wants to go to, and it rapidly shifts back and forth, causing a vibration, and it's the column of air inside the pipe that determines the pitch of the vibration. In the case of a reed pipe, it's the reed itself that determines pitch, and in the case of an electromagnetic driver, it's the frequency of magnetic pulsations that determines pitch, the length of the pipe coloring the sound.

    If the question is that you're not getting much bass until you reach a certain volume, I'd guess that under this certain volume, the vibrations are not loud enough to resonate with the enclosure. It must be that the enclosure increases bass by sympathetic resonance. Perhaps if the volume is too low, it fails to resonate.

    Wind pressure on flue pipes really has more to do with the characteristics of the flat sheet of air hitting the upper lip than it does with volume, although to a degree, more pressure makes more volume. But in the case of a resonant speaker enclosure, I would guess that more volume would not cause it to resonate into the overtone series ie. lose fundamental pitch and begin to resonate at an overtone. At least I don't think it would. I'm just guessing here.

    Let me know if this helps.

  13. #13
    Captain of Water Music Thomas Dressler's Avatar
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    Re: \' over blowing \'

    Thanks Julient! I was hoping for someone to answer who really knows for sure how this works. Now that I understand the reason for the question, I have a feeling it doesn't relate exactly, but since the question was asked, I did wonder how it works for sure.

    Thanks!

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    Re: \' over blowing \'

    Thanks Julien !

    >I'm thinking your speaker probably works more like a reed >pipe, where the pipe itself functions only as a resonator

    Right. The pipe is used to help support the bass frequencies.
    It is lower Q than an organ pipe plus usually stuffed to some extent to surpress the harmonics. The driver is also (in many instances) placed away from the end (so as not to excite selected harmonics)...........mike

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    Captain of Water Music Thomas Dressler's Avatar
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    Re: \' over blowing \'

    This is all very interesting. Have you ever listened to a 1920s Victor orthophonic victrola? Not the early ones, mind you, the orthophonic model, such as the Credenza, which was their premier model. Now there is an unbelievable example of acoustic reproduction! They'll knock your socks off even today.

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