The Study of Mode Transitons With an Artificilally Blown Clarinet

While learning the technique called voicing on a clarinet, one often experiences a squeak or grunt note. A squeak note is an undesirable, higher-pitched note that occurs without any change of the keys being pressed. Similarly, a grunt note is a lower-shifted note with the same circumstances. Voicing is a technique where one can draw out specific desirable frequencies of a note intentionally to play either a higher or lower note. The objective of this research is to study the conditions that cause squeak and grunt notes. A hermetically sealed box was built to hold the clarinet and simulate a mouth playing the clarinet. Placing the box at a positive gauge pressure of 6-12 psi and applying force to the reed makes the clarinet produce sound. A Polytech laser Doppler vibrometer was used to gather measurements of the vibration of the clarinet reed. Gauge pressures in the box ranging from 7 to 16 psi and several levels of force applied to the reed were studied. Preliminary data shows that squeak notes occur with air pressure between 15 and 16 psi and higher force on the reed. Grunt notes occur with air pressures between 6 and 12 psi and moderate force on the reed. The waveforms and spectra of the reed vibrations reveal the quantitative nature of the notes. Periodic waveforms with harmonic overtones show desirable, melodic sound, rich in timbre. Squeak notes have only one dominant peak and only one minor overtone, thus lacking in timbre. A grunt note shows many spectral lines, that are not harmonic and thus not melodic in timbre and closer to noise.