  Straight cylindrical stethoscopes serve as an important alternative to
conventional stethoscopes whose application in the treatment of infectious
diseases might be limited by the use of protective clothing. Yet their
miniaturization is challenging due to the low-frequency of bioacoustics signal.
Here, we design and experimentally implement a meta-stethoscope with
subwavelength size, simple fabrication, easy assembly yet high sensitivity,
which simply comprises multiple round perforated plate units and a cylindrical
shell. We elucidate our proposed mechanism by analytically deriving the
frequency response equation, which proves that the equivalent acoustic
propagation path is substantially increased by the high-index metamaterial,
enabling downscaling of the meta-stethoscope to subwavelength footprint. The
acoustic performance of meta-stethoscope is experimentally characterized by
monitoring the cardiac auscultation on clothed human body. The simulated and
measured results agree well, with both showing the expected enhancement of
sensitivity of our proposed meta-stethoscope (~ 10 dB) within the predicted
working frequency range from 80 to 130 Hz despite its compactness and
simplicity. Our designed portable, detachable yet effective meta-stethoscope
opens a route to metamaterial-enabled stethoscope paradigm, with potential
applications in diverse scenarios such as medical diagnosis and acoustic
sensing.
