With a name like "microphone," you'd expect something small—but perhaps not quite as small as this. Scientist have figured out how to use just one molecule to detect the vibrations from sound.

Although we talk about "hearing" rather than "feeling" sound, sound is made up of the physical vibrations through some medium, usually air but any other liquid or gas would do too. (And when those vibrations hit our eardrums, we perceive it as sound.) When those vibrations hit a single molecule of dibenzoterrylene (DBT), according to a new study published in Physical Review Letters, it fluoresces according to the sound's pitch.

To get that molecule of dibenzoterrylene to work as a microphone of sorts, scientists had to trap several molecules of it in a crystal of anthracene. When a sound wave gently rocks the crystal, DBT molecules are knocked around inside. This movement changes the interaction between the electron clouds of DBT and anthracene, which ultimately result in a slight shift in DBT's fluorescence. By tracking the fluorescence of just a single molecule of DBT, the scientists could track the frequency of the sound.


So what's the use of just a tiny and delicate acoustic sensor? Probably not much in your everyday life, since the setup needs to be very, very cold to work properly. (Air molecules at room temperature move around too much.) But this neat little feat could be put to use in physics labs, where researchers are looking for quantum effects in very small vibrating systems—a tiny sensor for tiny things. [New Scientist, American Physics Society]

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