The whirly tube, corrugaphone, or bloogle resonator, also sold as Free-Ka in the 1960s-1970s, is an experimental musical instrument which consists of a (ribbed) plastic tube or hose (hollow flexible cylinder), open at both ends and possibly wider at one end (bell), the thinner of which is rotated in a circle to play. It may be a few feet long and about a few inches wide. The faster the toy is swung, the higher the pitch of the note it produces, and it produces discrete notes roughly belonging to the harmonic series, like a valveless brass instrument generates different modes of vibration. However, the first and the second modes, corresponding to the fundamental and the second , are reported as being difficult to excite.[Sprott, Julien Clinton (2006). Physics Demonstrations: A Sourcebook for Teachers of Physics, Volume 1, p.158. "You can also use a corrugated plastic tube, called a 'corrugaphone,' 'Bloogle Resonator,' or 'Hummer,' to produce a variety of whistling sounds when you spin it around over your head. The frequencies are harmonics of the fundamental organ-pipe mode that are individually preferentially excited depending on the speed of rotation. It is hard to excite the fundamental and even the second harmonic, but the higher harmonics are easily excited." .] To be played in concert the length of the tube must be trimmed to musical tuning it.
According to the modified Hornbostel–Sachs organological system proposed by Roderic Knight
Sound
Hopkin describes a single whirled corrugaphone as capable of producing three or four different pitches.
[Hopkin, Bart (2009). Making Musical Instruments with Kids, unpaginated. See Sharp. .] Crawford describes harmonics two through
harmonic seventh as reachable while whirling, though seven takes, "great effort."
[Crawford, Frank S. (1974). " Singing Corrugated Pipes", AJP, Volume 42, pp. 278–81, Physics.umd.edu. "A corrugated tube open at both ends, with air flowing through the tube, sings notes which depend on the flow velocity and the length of the tube. The notes it sings are the natural harmonics of the tube."] Hopkin describes that with a corrugahorn, "with tubes of suitable length and diameters, the range extends well up the harmonic series, where the available tones are close together and you can, with practice, play quite
melody."
[Hopkin, Bart (1996). Musical Instrument Design: Practical Information for Instrument Making, unpaginated. See Sharp. .] In fact, since each sounding mode plays throughout a range of speeds (rather than at one specific speed), it is difficult to skip over harmonics, as this requires a jump in speed (rather than gradual change), though this is easily done using one's tongue and throat to interrupt the air flow with a corrugahorn.
Many sales offers describe the tubes as producing up to five distinct notes (presumably the
bugle scale: close to the harmonics 2, 3, 4, 5, and 6 ), and while higher modes may be possible, if hard work,
[" Sound Hose", SteveSpanglerScience.com.] dissonant adjacent harmonics may sound simultaneously, such as 15 and 16. The modes of a corrugated tube are usually lower than those of an uncorrugated tube of the same length and diameter, and, "audible vibration in the whirly tube appears only when air
flow velocity exceeds a certain minimum, which may preclude the sounding of the fundamental or lower harmonics."
[Crawford, Frank (1989). "What is a Corrugahorn?", Experimental Musical Instruments, Volume 5, pp. 14–9. Features description and illustration.] The
timbre of the notes produced by the whirly tube are, "almost all fundamental," according to
Fourier analysis (similar to
).
Tubes longer than many feet may have one end whirled while held near its middle or may be held out a car window.
The equations describing the sound produced when the tube is whirled, as proposed by F.S. Crawford in 1973, as follows, proposes that the air flowing through the corrugations should produce a sound similarly to a scraping instrument, such as a "reco-reco", in which a stick is scratched against a surface with regularly spaced grooves. This would be the rationale for the formulas below. However this tentative model is not experimentally demonstrated or supported by the theory of sounding pipes in acoustics.
\begin{align}
{} \\1pt
\text{flow velocity} & = \frac{\text{cm}}{\text{sec}} = \frac{\text{cm}}{\text{bump}} \times \frac{\text{bump}}{\text{sec}} \\6pt
& = \text{corrugation distance} \times \text{bump frequency}
\end{align}
Thus the faster the tube is swung or the more dense the corrugation the higher the pitch of the note produced.
According to Bernoulli's principle, as speed increases, pressure decreases; thus the air is sucked into the still or inside end of the tube as higher pressure air moves up the tube to fill the lower pressure air at the faster moving spinning or outside end of the tube.[" Whirly Tubes", ScienceWorld.ca.]
The characteristic speed is the mean flow through the pipe U and the characteristic length must be a multiple of the spacing between corrugations, nL, where n is an integer number and L is the distance between corrugations. At low speeds, the unstable interior flow needs to travel several corrugations to establish the feedback loop. As the speed increases, the loop can be established with fewer corrugations. The Strouhal number
was used as the scaling factor. A unique aspect of this whistle is that the internal flow carries both the unstable vortex downstream and the returning feedback signal upstream.
Use
A corrugated plastic tube whirling instrument became an instant, if short-lived, cultural phenomenon in late 1960s New York City under the name "Free-Ka", sold by street vendors, as captured by The New Yorker in 1970.
[" Free-Ka", by Robert MacMillan, The New Yorker, July 11, 1970, p. 20 "] It was used by
in the early 1970s in his production of
Shakespeare's A Midsummer Night's Dream.
[Barbara Hodgdon, p. 166, in "Shakespeare, Memory and Performance", ed. Peter Holland] It has been used by a number of artists including
Peter Schickele,
Frank Ticheli, Paul Simon, Macy Gray, Loch Lomond, and Yearbook Committee. Also in
Brett Dean's
Moments of Bliss (2004)
[Morris, Craig (August 7, 2009). " Whirly Tubes and Bloogles", LivMusic.com. ] and by The Cadets Drum and Bugle Corps in 2011. Donald Sosin's "137 Ridges" (1971) for flute, vibraphone and 15 tuned Free-kas was performed at the University of Michigan. It has been employed in some of
Peter Schickele's comic P. D. Q. Bach compositions such as the
Erotica Variations: IV (1979),
[" The Intimate P.D.Q. Bach", Schickele.com.][" Bach: Erotica Variations, for banned Instruments and Piano", PrestoClassical.co.UK.] Missa Hilarious (1975),
and
Shepherd on the Rocks with a Twist (1967).
Schickele, who calls it the
lasso d'amore (a pun on oboe d'amore), gives a tongue-in-cheek explanation of the instrument's evolution: 18th century Viennese cowboys twirled "their over their heads with such great speed that a musical pitch was produced. . . . The modifications that had made this development possible rendered the useless for roping cattle."
[Schickele, Peter. "'Erotica' Variations for banned instruments and piano, S. 36EE" The Intimate P.D.Q. Bach, Vanguard, LP, VSD 79335, 1974. On this recording, Schickele additionally claimed they were 18th century Viennese Cowboys, meaning they likely performed at the Winter Riding School.]
David Cope, in 1972, discussed a cugaphone, which, in 1997, he describes as an instrument built from a trumpet mouthpiece attached to a long piece of 3/8-inch bore plastic tubing with a kitchen funnel, usually in hand, at the other end acting as the bell; thus sound may be modulated by directing the funnel, applying pressure to the funnel, or by swinging the funnel around one's head and creating a Doppler effect.[Cope, David (1997). Techniques of the Contemporary Composer, p.146. Schirmer. . Cites: Cope, David (1972). Margins. New York: Carl Fischer.] This version of the instrument would require brass embouchure technique rather than corrugation. By 1997 ensembles of cugaphones existed.[Cope (1997), p.148.]
The inventor is not known, though Bart Hopkin credits the late Frank Crawford of the UC Berkeley Department of Physics with, "developing the idea and researching the underlying acoustics,"[Sanders, Robert (2003). " Physicist Frank Crawford, who worked on bubble chambers, supernovas and adaptive optics, has died at 79", Berkeley.edu.] This requires a tube with a diameter smaller than commonly marketed as toys (a one inch diameter is too great, a half-inch is not),
See also
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Bullroarer: traditional long-distance communication instrument that makes a low roar when swung in a circle
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Boomwhacker: lightweight, hollow, plastic tube, tuned to a musical pitch by length
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Laminar–turbulent transition
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Pipe flow
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Whipcracking
Further reading
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Nakiboğlu G, Rudenko O, Hirschberg A. "Aeroacoustics of the swinging corrugated tube: voice of the Dragon" J Acoust Soc Am. 31, 749–765, 2012.
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Rajavel, B., Prasad, M.G. "Parametric studies on acoustics of corrugated tubes using large eddy simulation (LES)", Noise Control Engineering Journal, 62(4), 2014.
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Lisa R., Taylor, M.E., "Experimental Study of the Acoustical Characteristics of Corrugated Tubing", Noise and Vibration Control Laboratory, Stevens Institute of Technology, Thesis 1994.
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(1974). " Corrugahorns Scientific American, Volume 230". Munn & Co.
External links
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, "Go Tell It on the Mountain"
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" Corrugaphone" instrument description, University of Wisconsin – Madison Physics Department.
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" Whirly", Exo.net.
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" Freq Tube ", Faraday.Physics.UIowa.edu. Includes bibliography.
