American Band College David Rachor, Bassoon Clinician, June 2007 Wind Acoustics and other Important Principles

1. Overtone series: octave, fifth, fourth, major third, etc 2. 20-20,000 Human hearing limits, 20-20K Hz. 3. Human Nerve Smear Factor Human nerve recovery time, 20 times a second 4. Sound waves and how they affect woodwinds 1) Octave vents destroying bottom octave, or 12th in case of clarinet 2) Octave vents need to be a nodal point of bore. These are usually misplaced. 3) Octave vents put in compromise position because one cannot have a vent for each note. e.g. 6 fingered note on woodwinds usually out-of-tune 5. Missing bore (Phantom bore) of conical bore woodwinds This is the volume from the beginning of the bore to the apex of the cone. 6. Conical Bore Woodwinds: Oboe, Bassoon, Saxophone Over-blow octave Do not easily respond softly in low range 7. Cylindrical Bore Woodwinds. Two types, open and stopped Open: Flute Easily responds softly in low range. Changes octave easily Stopped: Clarinet Easily responds softly in low range 8. Basic double reed acoustics Equivalent volume of reed This volume replaces the volume of the missing bore. Since both walls are made of cane, double reeds are a flexible system. Changing embouchure pressure against the reed blades can change the equivalent volume of the reed. Single reeds systems only have one flexible wall. Resonance frequency of reed This is the normal vibrating pitch of the reed, this is also flexible. The player changes this pitch by air/embouchure manipulation. If this pitch is general is too high, the pitch of the instrument will be sharp. 9. Bouncing embouchure On the bassoon, the player can move the embouchure when tonguing. This is a form of air/embouchure balance adjustment and therefore does not affect pitch. 10. Bore Length as compared to Bore diameter Woodwinds: short bore in relation to bore diameter means that the instrument does not change partials easily. Why octave vents are needed. Brass: long bore in relation to bore diameter means that instrument does change partials easily. 11. Tone-hole lattice Very important to the way a woodwind instrument plays. The bassoon sounds like a bassoon because of the long, narrow tone holes on the wing and boot joints. These were developed in the 16th century before keys were invented to be able to close the tone holes on a long, bass instrument. Cut-off Frequency; In short, all frequencies below this frequency are reflected back up the bore toward vibrating source and produce standing waves, all frequencies below this cut-off pass down the bore. The bassoon has a low cut-off frequency,

1 about 600 Hz. Size and spacing of the tone holes and in the case of the bassoon the long and narrow tone holes determine this frequency. To lower pitch, close a tone-hole below the first open tone-hole To raise pitch, open a tone-hole below the first open tone-hole

Further Reading: Murray Campbell and Clive Greated The Musician’s Guide to Acoustics Oxford, 1987

Donald E. Hall Musical Acoustics: An Introduction Wadsworth, 1980 Arthur Benade Fundamentals of Musical Acoustics Second, Revised Edition Dover, 1990

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