Vibrotactile rendering on a touch surface with reduced sound radiation

Vibrotactile feedback has been utilized in various electronic devices with interactive touch surfaces to improve the tactile interaction between the user and the touch surface. Recent studies have proposed vibration rendering methods that enable specific vibration patterns to be generated at desired positions on a touch surface. However, the vibration rendering causes the surface to radiate considerable acoustic noise, which can deteriorate the overall quality of the haptic interaction. This paper proposes a vibration rendering method that reduces the sound radiation from vibrating touch surfaces. In the proposed method, a vibroacoustic model of a touch surface system, combined with measured frequency response functions, is utilized to predict the vibration responses and sound radiation generated by actuator driving signals. Subsequently, a constrained optimization problem is formulated to obtain the optimal driving signals that minimize the estimated sound radiation while rendering a target vibration pattern at desired positions. To validate the proposed method, vibration rendering experiments were conducted on an experimental touch surface system. The driving signals obtained through the proposed method accurately rendered a complex target vibration pattern at the desired positions on the touch surface. Compared to an existing vibration rendering method, the proposed method reduced the estimated sound radiation by 5.1 to 12.3 dB, without structural modifications and hardware additions.