Low-loss ultrasound transmission through glass assisted by resonance

Hallvard Angelskår; Christopher Andrew Dirdal; Tron Vedul Tronstad; Tom Kavli; Andreas Vogl

doi:10.1016/j.ultras.2019.01.011

Low-loss ultrasound transmission through glass assisted by resonance

Ultrasonics. 2019 Jul:96:160-164. doi: 10.1016/j.ultras.2019.01.011. Epub 2019 Jan 31.

Authors

Hallvard Angelskår¹, Christopher Andrew Dirdal², Tron Vedul Tronstad³, Tom Kavli⁴, Andreas Vogl²

Affiliations

¹ SINTEF Digital, Dept. of Microsystems and Nanotechnology, Gaustadalléen 23C, 0373 Oslo, Norway. Electronic address: hallvard.angelskar@sintef.no.
² SINTEF Digital, Dept. of Microsystems and Nanotechnology, Gaustadalléen 23C, 0373 Oslo, Norway.
³ SINTEF Digital, Dept. of Connectivity Technologies and Platforms, Strindveien 4, 7030 Trondheim, Norway.
⁴ Elliptic Laboratories AS, Akersgata 32, 0180 Oslo, Norway.

PMID: 30771908
DOI: 10.1016/j.ultras.2019.01.011

Abstract

We have investigated transmission of ultrasound signals from a speaker in air through a 400 µm thick borosilicate glass plate, similar to those found in consumer electronics products such as mobile phones and tablets. In order to enhance transmission, we took advantage of resonances in the glass plate and a cavity, which is placed between the glass and the microphone. The results show that it is possible to achieve transmission of a signal with bandwidth of approximately 5 kHz with less than -10 dB attenuation, and only -2 dB attenuation at the resonance peak frequency. With more optimized assembly the attenuation can be further reduced. Finite element simulations and analytical considerations show that there are two main resonance peaks, attributed to the glass resonance and cavity resonance, respectively. The geometry can be tuned to exploit the synergy of these two resonances in order to tailor the peak frequency, the bandwidth and to optimize transmission.

Keywords: Cavity; Plate; Resonance; Through-glass; Touchless; Transmission.