terça-feira, 25 de dezembro de 2012

Included papers


          1. Included papers

          The present dissertation comprises a summary and the following papers, listed in systematic order. Click to read the abstract of each one. The available papers are undelined, just click to load them.

          Paper I Leonardo Fuks & Johan Sundberg (1996): "Blowing pressures in reed woodwind instruments", KTH TMH-QPSR 3/1996, 41-57, Stockholm, to appear in a revised and modified version as "Blowing pressures in bassoon, clarinet, oboe and saxophone", in press for Acustica/acta acustica.

          Paper II Leonardo Fuks (1998): "Aerodynamic input parameters and sounding properties in naturally blown reed woodwinds", KTH TMH-QPSR 4/1998, 1-11, Stockholm

          Paper IIIa Leonardo Fuks (1996): "Prediction of pitch effects from measured CO2 content variations in wind instrument playing", KTH TMH-QPSR 4/1996, 37-43, Stockholm

          Paper IIIb Leonardo Fuks (1997): "Prediction and measurements of exhaled air effects in the pitch of wind instruments", Proceedings of the Institute of Acoustics, ISMA'97 Conference, Edinburgh, Vol. 19: Part 5 (1997), Book 2, 373-378

          Paper IV Leonardo Fuks & Johan Sundberg (1998): "Respiratory inductive plethysmography measurements on professional reed woodwind instrument players", KTH TMH-QPSR 1-2/1998, 19-42, to appear in a revised and modified version as "Using Respiratory Inductive Plethysmography for Monitoring Professional Reed Instrument Performance"; in press for Medical Problems of Performing Artists, March 1999

          Paper V Leonardo Fuks (1998): "Assessment of blowing pressure perception in reed wind instrument players", KTH TMH-QPSR 3/1998, 35-48, Stockholm, submitted for publication

          Paper VI Leonardo Fuks, Britta Hammarberg & Johan Sundberg (1998): "A self-sustained vocal-ventricular phonation mode: acoustical, aerodynamic and glottographic evidences", KTH TMH-QPSR 3/1998, 49-59, Stockholm


          Paper I Blowing pressures in reed woodwind instruments

          The blowing pressures during wind instruments playing have not been systematically measured in previous research, leaving the dependencies of pitch and dynamic level as open questions. In the present investigation, we recorded blowing pressures in the mouth cavity of two professional players of each of four reed woodwinds (Bb clarinet, alto saxophone, oboe, bassoon). The players performed three different tasks: (1) a series of isolated tones at four dynamic levels, (2) the same series with a crescendo-diminuendo tones and (3) ascending-descending musical arpeggio played legato at different dynamic levels (pp, mp, mf, ff). The results show that, within instruments, the players' pressures exhibit similar dependencies of pitch and dynamic levels. Between instruments, clear differences were found with regard to the dependence on pitch.

          Paper II Aerodynamic input parameters and sounding properties in naturally blown reed woodwinds

          Input aerodynamic parameters in reed woodwinds - oboe, alto saxophone, bassoon and clarinet - were measured when professionals played different pitches at three dynamic levels. Two reeds were used, one rated as a hard and another as a soft reed. The tasks consisted of playing long sustained tones with and without vibrato. Audio and blowing pressure signals were recorded. Lung volume variations were indirectly measured by a spirometric procedure, which also showed the average air consumption, i.e. the mean airflow. The tones were played in a laboratory room and also in a calibrated reverberant chamber allowing estimation of radiated sound power. Average values for flow resistance, aerodynamical power and mechanical efficiency were computed. Airflow and input power varied con-siderably between instruments and between the two reed types, but generally increased with sound level. For vibrato tones produced on oboe, bassoon and saxophone, wide pressure oscillations were observed, on average 10 cm H2O for the oboe and bassoon, and reaching values of 20 cm H2O in some cases. Possible origins of these pressure variations are discussed.

          Paper IIIa Prediction of pitch effects from measured CO2 content variations in wind instrument playing

          The effect of carbon dioxide (CO2) exhaled by wind instrument players on the resulting pitch is investigated. A theoretical-numerical approach is applied to determine the dependence of sound velocity on the percentage of CO2 contained in the air. Realistic performance data were obtained from experiments in which a professional musician played a clarinet and an oboe, while the CO2 content of exhaled air was recorded together with the audio signal. By calculating the impact of the variation of CO2 and O2 contents on sound velocity, considerable effects on the fundamental frequency of the tones produced are predicted.

          Paper IIIb Prediction and measurements of exhaled air effects in the pitch of wind instruments

          The natural resonance frequencies of wind instruments are dependent on the geometry of the air column, the dimensions and design of reed/mouthpiece, the placement and size of toneholes and the sound speed in the gas inside the instrument. Also, this gas continuously changes in composition with respect to the content of carbon dioxide (CO2) and oxygen gas (O2) due to the player's metabolic activity. These changes should affect the fundamental frequency to some extent. This frequency is also a function of the embouchure configuration and the highly varying blowing pressures . The purpose of the present study was to provide an experimental and theoretical basis for analysis and measurement of the impact of the gas changes in the sounding pitch.
          Typical atmospheric air contains a concentration of CO2 ranging between 0.03% and 0.06%, while O2 is found at a percentage of approximately 20.9 %, regardless of local altitude. These are the gases whose percentages change between inhaled and exhaled air. In addition, there is metabolic production of water, which is expelled as saturated vapour. It is also important to note that the respiratory airways comprise a volume defined between the air inlet and the first pulmonary structures, called anatomical dead space, in which the air practically does not change in composition from the ambient values. The anatomical dead space is in average ca. 150 ml. Variations in exhaled CO2 during performance of a solo work with the oboe and sustained tones with the clarinet have been previously documented. The results showed that in wind instrument playing, the CO2 contents in the pulmonary air may vary considerably with time, roughly from 2.5% just after a deep breath up to 8.5% after a long playing period of ca one minute. The O2 contents in the alveolar gas, thus the air to be exhaled, are reported to achieve a minimum value of 14%.

          During playing wind instruments such as the oboe and the clarinet, the content of CO2 in the expired air varies between the ambient level and up to 8.5% in extremely long phrases, while for the O2 it may vary from the ambient 21% down to 12%, or even less. The increase in CO2 tends to decrease the pitch and the fall in O2 tends to increase pitch. Even then, due to differences in gas properties and the rate with which the gases vary, the total effect is that of pitch decrease. This effect may account for a fall in fundamental frequency of the tones by more than 20 cents. Although we could presume that the pitch effects induced by gas variation are compensated for by the player by means of varying embouchure, blowing pressure and other playing characteristics, this effect still seems a relevant factor in wind instrument playing.

          Paper IV Respiratory inductive plethysmography measurements on professional reed woodwind instr. players

          Respiratory movements and lung volume variations during natural performance of wind instrument playing have been scarcely documented in the literature, but may provide a deeper insight into performance techniques, players' physiological characteristics as well as into the physics of the instruments. Using Respiratory Inductive Plethysmography (RIP) respiratory movements of eight professional players (oboe, clarinet, alto-saxophone, bassoon) were measured during playing of exercises and orchestral solo voices. Calibration of the relative contribution of abdominal wall and rib cage regions was achieved from isovolume manoeuvres. Pneumotachometry was applied for absolute calibration of the RIP. Flow through a standard aerodynamic resistance at constant pressure was used for assessing the method of measurement under dynamic conditions. Different possible artifacts are described and discussed. The method yielded linear and accurate results, provided that significant body movement is absent, appeared to be non-disturbing to the musicians, accurate and robust. Depending on instrument and piece the players initiated the breath groups at 55% - 87% and terminated them between 14% - 52% of their vital capacity. Unlike what has been found for singers, the players generally showed simultaneous and in many cases equally important contributions from rib cage and abdominal wall during playing. In extreme cases, inhalations were achieved in approximately 300 ms and reasonably synchronised with the RIP signals.

          Paper V Assessment of blowing pressure perception in reed wind instrument players

          Perception of blowing pressures in eight reed instrument players was assessed by means of a psychophysical production method. The aim of the study was to investigate how the players judge mouth pressures independently from playing conditions, i.e., without embouchure effort, reed vibration, airflow or auditory feedback. Reference pressures were established by relaxation at three lung volume levels ranging between just above functional residual capacity (FRC) to nearly full lungs. Successive doubling estimates were employed to assess the relationship between pulmonary pressure - a physical variable, and perceived pressure - a psychophysical variable. Regression analysis was applied to the data under four different models - linear, logarithmic, exponential and power functions. Generally, the linear model was the one that presented a highest correlation with the experimental data (r2=0.943), while the logarithmical model (Fechner Law) corresponded to a lowest correlation (r2= 0.869). The power function exponents (Stevens Law, r2=0.924) varied considerably among subjects, with a global average of 0.94, and among the three increasing lung volume levels, 0.79, 0.92 and 1.13, respectively. The method provided consistent data from the subjects and the results provided information about this rarely studied modality.

          Paper VI A self-sustained vocal-ventricular phonation mode: acoustical, aerodynamic and glottographic evidences

          This investigation describes various characteristics of a particular phonation mode, vocal-ventricular mode (VVM), as produced by a healthy, musically-trained subject. This phonation mode was judged as perceptually identical to that used in the Tibetan chant tradition. VVM covered a range close to an octave, starting at about 50 Hz. High-speed glottography revealed that the ventricular folds oscillated at half the frequency of the vocal folds thus yielding a frequency of f0/2. Phonation at f0/3 was also possible. Presumably, aerodynamic forces produced by the glottal flow pulses sustained the vibrations of the ventricular folds. Complementary aspects of this type of phonation were compared to phonation in modal and pulse registers by acoustical analysis of the audio signal, by inverse filtering of the flow signal and by electroglottography (EGG). In addition, oesophageal pressures were measured. These analyses revealed that every second flow pulse was attenuated because of the ventricular fold vibrations and that the laryngeal contact area alternated between two minimum values. The spectra of VVM sounds contained clear harmonic partials up to about 4 kHz. Oesophageal pressure tended to change when phonation switched between VVM and modal phonation. Examples of periodic pulse register, another case of voice period multiplication, produced patterns of EGG waveform differing from those of VVM. The possibilities of using VVM in contemporary music, whether in a purely vocal form or during to wind instrument playing, are discussed.

          ©1998 by Leonardo Fuks

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