CAJ | 학술논문

通常认为，当气室压力提高到一定程度，调制气流声源声压级输出将趋于饱和。为了从基本原理上探讨进一步提高声源输出的途径，设计了收缩-扩张喷口，将调制作用上游的声速流动提高至超声速。理论分析表明，来流气压较高时，超声速调制优于声速调制，可获得一定的声压级增益。增益量随喷口面积比减小而增加。旋笛实验在调制频率较低时得到了超声速调制的声压级增益；调制频率较高时，受瞬态作用的影响，参与调制的气流很可能未完全发展为超声速流动，超声速调制与声速调制的旋笛性能相同。
통상인위，당기실압력제고도일정정도，조제기류성원성압급수출장추우포화。위료종기본원리상탐토진일보제고성원수출적도경，설계료수축-확장분구，장조제작용상유적성속류동제고지초성속。이론분석표명，래류기압교고시，초성속조제우우성속조제，가획득일정적성압급증익。증익량수분구면적비감소이증가。선적실험재조제빈솔교저시득도료초성속조제적성압급증익；조제빈솔교고시，수순태작용적영향，삼여조제적기류흔가능미완전발전위초성속류동，초성속조제여성속조제적선적성능상동。
It is generally acknowledged that the sound pressure level (SPL)of air-modulated speaker (AMS)will finally reach the level of saturation when the chamber pressure increases to a certain degree.As a new approach to obtain higher SPL output,supersonic flow modulation was discussed in which the flow speed of nozzle exit was increased from sonic to supersonic.Results from the quasi-steady theory proved that,when the chamber pressure is high,the SPL in the supersonic case is higher than that in the sonic case.Larger SPL increments generally appear at smaller nozzle area ratio.The improvement of the source intensity was validated by the comparison of sound measurements between the sonic and supersonic cases in low frequency modulation.But in high frequency modulation,due to the transient flow effect,the SPL in the supersonic case is the same as that in the sonic case while the air jet is considered to be not fully developed or sped up to be supersonic.