An effective boronizing process to titanium diaphragm has been developed. The process provides a diaphragm with large specific modulus of elasticity and bending stiffness. Titanium diaphragms are buried in a mixed powder of boron (70wt%), carbon black (20wt%) and sodium carbonate (10wt%) and heated at a required temperature for a required time under 1Pa pressure. By this process, Young's modulus of boronized titanium sheets with 25μm and 35μm thickness are brought up to 2. 5×10''N/m^2 and 2. 3 × 10''N/m^2 respectively. Density of boronized titanium sheets is about 4. 5×10^3kg/m^3, which is almost equal to the density of titanium. Cross section of boronized titanium sheet consists of TiB_2 surface layer, TiB spike and Ti layer which is located in the middle of the section. High frequency resonance of 2. 5 cm diameter dome type loudspeaker with boronized diaphragm reaches to 37kHz which is about 1. 5 times higher than that of the titanium diaphragm loudspeaker with same shape. 12cm cone type loudspeaker using the boronized diaphragm has flatter and wider frequency response and lower harmonic distortion than that of titanium diaphragm loudspeaker with same shape.
In this paper, the properties of Rayleigh wave propagation on two- or three- layered structures using LiNbO_3, LiTaO_3 and SiO_2 are studied theoretically and experimentally. The properties of the SiO_2/(ZY)LiNbO_3 structure relevant to Rayleigh wave propagation are studied, and it is shown that the piezoelectric coupling coefficient is 3. 8% with a zero temperature coefficient of the delay. It is theoretically found that the LiTaO_3 layer has the property of a wave guide and the poynting power is concentrated in the LiTaO_3 layer in the SiO_2/(ZY)LiNbO_3 structure. Furthermore, the approximate equation of temperature coefficient of the wave velocity for multi-layered structures is proposed. The coefficient of linear expansion of the substrate has been usually used for the approximate value of that of a layered structure. In this paper, the coefficient of linear expansion of the layered structure is theoretically investigated. Experimentally the insertion loss (or the piezoelectric coupling coefficient) and the temperature coefficient as a function of the SiO_2 thickness are measured for the SiO_2/(ZY)LiNbO_3 and the SiO_2/(ZY)LiTaO_3/(ZY)LiNbO_3 structures. The zero temperature coefficients can be obtained for both structures.
Statistical energy analysis is used to predict the internal sound pressure and the external of a rectangular enclosure with five flexible panels except a base pane, such as the acoustical enclosure, when the enclosure is excited by the structure-borne sound. The spatial average of the time-mean-square velocity measured on five panels is used to obtain those sound pressures. It is shown that the external sound pressure near the panel can be computed as the sum of the sound radiation power due to the flexural vibration and the non-resonant sound transmission power of the panel, if the receiving room is assumed to be the free space or the anechoic room. The noise reduction produced by a rectangular enclosure can be obtained from the ratio of the internal sound pressure to the external. The ratio of the non-resonant sound transmission power from the test panel to the sound radiation power from the same area of the infinite rigid panel (such as the piston) having the same velocity with the panel is computed, and the apparent sound radiation efficiency, that is, the sum of the sound radiation efficiency and this ratio is introduced. For the noise reduction and the apparent radiation efficiency, experimental results are compared with theoretical predictions with generally good agreement.
The changes in the normal modes and the displacements due to forced vibration of the conical cone and the convex cone, resulting from the voice coil and the outer surround, are calculated by the finite element method. And the sound pressure response is calculated using the displacements. The displacement and the area between the innermost nodal circle and the next outer nodal circle of the cone mainly contribute to the formation of the sound pressure peaks. Attachment of the voice coil and the surround cause the shift to the nodal circles. An inward shift is resulted from the voice coil, and an outward shift is resulted from the surround. These shifts cause the change of area and displacement and the change of peak sound pressure level. In the conical cone, the attachment of the voice coil causes the change of the peak sound pressure level in the normal modes, a large increase in the 1st and 2nd order, a slight change in the 3rd order, and a large decrease in the 4th and higher order. The another attachment of the surround causes the change of the peak sound pressure level, a large decrease in the 1st order, a slight increase in the 2nd order, and a slight decrease in the 3rd and higher order.
It is an essential feature in surface acoustic wave (SAW) device applications to know the propagation characteristics. In this paper, the characteristics of Rayleigh waves on LiNbO_3 are computed by changing arbitrarily both cut and propagation direction. The results are shown in a set of maps of equal velocity, equal power flow angle, equal electro-mechanical coupling constant and equal temperature coefficient of delay time. From theses maps it is possible to know the characteristics of SAW propagation for every substrate with arbitrary cut and propagation direction. Therefore these maps are very useful for the selection of new substrate of LiNbO_3. According to the computed results, the maximum value of electro-mechanical coupling constant K^2 is 5. 68% and temperature coefficient of delay time is greater than 70ppm/℃ for every cut.