Why does Achelous have such a high THD peak at 10 kHz?
The THD peak at ~10 kHz stems mainly from a mode of the MEMS at 21 kHz. When the MEMS is excited with 21kHz it resonates strongly and produces movement and subsequently a higher SPL. Due to small inherent non-linearities in the movement of the MEMS, 10.5 kHz will produce a small frequency component at 21 kHz which resonates and gets amplified, resulting in a mathematically high THD value at 10.5 kHz.
Want to read more about THD measurement? Check out our whitepaper.