Ultrasound emitted from an array of transducers can produce various tactile sensations by temporally controlling the phase and amplitude of the transducers. However, the controllability in haptic applications has not been well examined. This article clarifies a phase shift of the driving signal causes amplitude fluctuation of emitted ultrasound, even under a constant driving amplitude. We demonstrate theoretically that this problem exists in general resonant systems with various quality factors, and point out that it produces radiation force decrease and audible noise. We also show a method to reduce the fluctuation and quantitatively evaluate the effectiveness. The results provide the measure of the displayed force fluctuation by a fast focus movement and enable silent haptic stimulation.

中文翻译：

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通过空中超声触觉中的逐渐相移减少幅度波动

从换能器阵列发出的超声波可以通过暂时控制换能器的相位和振幅来产生各种触觉。然而，触觉应用中的可控性尚未得到很好的检验。这篇文章阐明了驱动信号的相移导致发射超声的振幅波动，即使在恒定的驱动振幅下。我们从理论上证明了这个问题存在于具有各种品质因素的一般谐振系统中，并指出它会产生辐射力降低和可听噪声。我们还展示了一种减少波动和定量评估有效性的方法。结果提供了通过快速焦点移动显示的力波动的测量，并实现了无声的触觉刺激。