| Summary: | 碩士 === 國立宜蘭大學 === 自然資源學系碩士班 === 96 === The objective of this study was to investigate the effects of tube length on the it’s air resonance frequency for plastic pipes and applied to the tunning of bamboo xylophone and bamboo marimba. Plastic pipes and Moso bamboo or Makino bamboo were used as expermental materials and Fast-Fourier-Transformation(FFT) spectrum analyiser was used to determined the air resonance frequency of tubes and the bamboo body vibration frequencies.
Tunning process criteria and chart were then established for bamboo xylophone and bamboo marimba maker for fine tunning. Research results showen that the air resonance frequencies from 10.79cm, 5.50cm, and 3.02cm plastic pipes were significantly different at 95% confidence level with respect to ANOVA statistical analysis. T test approach was applied to examined the difference of air resonance of plastic pipe in same diameter category and no significan difference was founded. Therefore, single test specimen with regard to different diameters was used to investigate the influence of tube height of pipe on it’s air resonance frequency. Resuts also showen that the air resonance frequency with 10.79cm in diameter of bamboo marimba type plastic pipe was the lowest among three. Similar result was founded in the bamboo xylophone type plastic pipe. When the tube height and diameter were same, the air resonance frequencies for the plastic pipe in bamboo xylophone shape was slightly higher than those pipes shaping based on of bamboo marimba. This probally bcaused the bamboo marimba had two tongue on both side but te bamboo xylophone had only one tongue on a single side. Due to the tongue on both side elongate the length of tube length decrease the air resonance frequency of bamboo marimba pipes. Due the knot edges in the bamboo pipe decrease the effective diameter ,
the air resonance frequencies of bamboo pipes were slightly higher than plastic pipes. High correlationship were found between air resonance frequencies and tube length. The determination coefficients of regression equation with regard to 10.79cm, 5.50cm, and 3.02cm in diameter were 0.976, 0.993, and 0.998, respectively. This suggested that tube length derived from plastic pipe study could be reasonably applied to predicted the tube length of bamboo pipe at certain air resonance frequency. Tube lenght determined by TBLCURVE software were close to those pipes by real tuning process. The locations of antinode of fundamental bending vibration mode of bamboo xylophone located at two ends, but located at the end of pipe-tongue for bamboo marimba. The verification of locations of antinode and node from modal analysis could be useful for the perfromance and tuning of bamboo instruments.
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