Investigating Amplitude Modulation Effects on Wide Bandwidth & High SPL Sc0.3Al0.7N MEMS Ultrasonic Speakers

Investigating Amplitude Modulation Effects on Wide Bandwidth & High SPL Sc0.3Al0.7N MEMS Ultrasonic Speakers

2025 IEEE International Ultrasonics Symposium (IUS)

10.1109/IUS62464.2025.11201594

https://doi.org/10.1109/ius62464.2025.11201594

David Sze Wai Choong, Yu Feng Thien, Prakasha Chigahalli, Duan Jian Goh, Shyam Trivedi, Jihang Liu, Yong Shun Teo, Hong Yan, Daniel Chen, Yul Koh, Alberto Leotti, Chang Kwan Teo, Silvia Adorno

Electrical and Electronic Engineering

20 October 2025

Choong, D. S. W., Thien, Y. F., Chigahalli, P., Goh, D. J., Trivedi, S., Liu, J., Teo, Y. S., Yan, H., Chen, D., Koh, Y., Leotti, A., Teo, C. K., & Adorno, S. (2025). Investigating Amplitude Modulation Effects on Wide Bandwidth & High SPL Sc0.3Al0.7N MEMS Ultrasonic Speakers. In (Editor), 2025 IEEE International Ultrasonics Symposium (IUS). https://doi.org/10.1109/ius62464.2025.11201594

In this work, we investigate the performance of 30% scandium-doped aluminum nitride (ScAlN) MEMS devices for transmitting audible-range sounds and enhancing low-frequency bass response using amplitude modulation (AM). The baseline 4 × 5 array device, with a 22 kHz resonance, exhibits limited acoustic power below 1 kHz, producing 90 dB SPL (sound pressure level) compared to 126 dB SPL at resonance. By applying varying AM depths, we demonstrate an increase in SPL at lower frequencies, reaching 120 dB SPL. Audio signals captured using a high-resolution ear simulator were post-processed to assess total harmonic distortion (THD), revealing a substantial improvement—from 112.3% without AM to 0.54% with AM. These findings highlight AM as an effective approach to extending low-frequency performance and reducing distortion in ScAlN MEMS acoustic devices.

Publisher Copyright

This research / project is supported by the ASTAR - Piezo Specialty Lab-in-Fab 2.0
Grant Reference no. : I2301E0027

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https://oar.a-star.edu.sg/communities-collections/articles/23324

amplitude modulation

Institute of Microelectronics