• The Journal of the Acoustical Society of Korea
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• v.25 no.3
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• pp.101-106
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• 2006

In this study, the impedance behavior of micro-speaker had been investigated as a function of hole area existing on the grille. In order to theoretically study the change of acoustical property due to the different total hole area, the holes were treated as a short open pipe system, such as an orifice. This theoretical result was in an excellent agreement with the experimental one. In detail, the acoustic impedance to be caused by the hole could be greatly increased with the decrease of hole area. Therefore, it can be concluded that the acoustic property of micro-speaker could be greatly changed by increasing the acoustic impedance of hole with reducing hole area.

• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.987-994
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• 1993

Inductive and resonance effects play an important role in determining carbony) stretching frequencies of ketones. Hydrogen bonding, dielectric effects, and steric effects are all factors which determine the carbonyl stretching frequency, νC=O of ketones in solution. The $ν_{C=O}$ frequencies were shifted by approximately 27$cm^{-1}$ each by substituting to a phenyl group for a methyl group in acetone. The $ν_{C=O}$ frequency for ketones shifted differently in various solvents and increased with increasing the volume ratio of the ketones in water solutions. The $ν_{C=O}$ frequency for ketones shifts continously at constant concentration of ketone in solutions of $(CH_3)_2SO/CCl_4$and$CHCl_3/CCl_4$ with changing of the mole ratio of two solvents. The $ν_{C=O}$ frequency was also affected by changing concentration in either $CCl_4$ or $(CH_3)_2SO$ solution and in either $CCl_4$or $CHCl_3$ solution.