Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
a SPL test results with a driving voltage of 2.5 Vrms. b–e Comparison of the proposed speaker with other designs9,14,28,34 in terms of b normalized SPL, c FOMvol, d normalized sensitivity, and e FOMsen