Sound emission from the ear triggered by single molecules?

If a human ear is stimulated with short sound pulses an acoustic response can be recorded many milliseconds later in the ear canal. This 'cochlear echo' was discovered by Kemp some years ago. Soon after this discovery it was found that many normal ears also emit weak sounds without being stimulated. Here we present the results of the measurements of minimum stimulus energy needed to influence this acoustic emission process. This energy is so low (1 eV) that processes at the molecular level are likely to play an important role. This may have consequences for theories of normal cochlear functioning.