Lamb-wave (X, Y) giant tap screen panel with built-in microphone and loudspeaker
Abstract
This paper presents a passive (X, Y) giant tap screen panel (GTP). Based on the time difference of arrival principle (TDOA), the device localizes low-energy impacts of around 1 mJ generated by fingernail taps. Selective detection of A0 Lamb waves generated in the upper frequency spectrum, around 100 kHz, makes it possible to detect light to strong impacts with equal resolution or precision, close to 1 cm and 2 mm, respectively, for a 10-mm-thick and 1-m$^2$ glass plate. Additionally, with glass, symmetrical beveling of the edges is used to create a tsunami effect that reduces the minimum impacting speed for light taps by a factor of three. Response time is less than 1 ms. Maximum panel size is of the order of 10 m$^2$. A rugged integrated flat design with embedded transducers in an electrically shielding frame features waterproof and sticker/ tag proof operation. Sophisticated electronics with floating amplification maintains the panel at its maximum possible sensitivity according to the surrounding noise. Amplification and filtering turns the panel into a microphone and loudspeaker featuring 50 mV/Pa as a microphone and up to 80 dB$_{lin}$ between 500 Hz and 8 kHz as a loudspeaker.