Physicists at the Nanosystems Initiative Munich (NIM) have managed to detect sound waves at minuscule length scales. Their nanoear is a single gold nanoparticle that is kept in a state of levitation by a laser beam. Upon weak acoustic excitation the particle oscillates parallel to the direction of sound propagation.
The nanoear is capable of detecting sound levels of approximately -60 dB. Thus, it is about a million times more sensitive than the hearing threshold of the human ear, which by convention is set at 0 dB.
In this way, the nanoear could yield important information on the minute motions of cells, cell organelles or artificial microscopic objects. Additionally, no high-end devices are necessary as only well-established methods are used.
Also: Learn about hearing and manufacturing in the digital age.