After Beethoven went deaf, he found he could affix a metal rod to his piano and bite down on it while he played, enabling him to hear perfectly through vibrations in his jawbone. The process is called bone conduction

Ludwig van Beethoven was a German composer and pianist. A crucial figure in the transition between the Classical and Romantic eras in Classical music, he remains one of the most recognized and influential of all composers. His best-known compositions include 9 symphonies, 5 piano concertos, 1 violin concerto, 32 piano sonatas, 16 string quartets, a Mass the Missa solemnis, and an opera, Fidelio.

Beethoven is reported to have dated his hearing loss from a fit he suffered in 1798 induced by a rage at the interruption of his work—having fallen over, he got up to find himself deaf. His hearing only ever partially recovered and, during its gradual decline, was impeded by a severe form of tinnitus. As early as 1801, he wrote to friends describing his symptoms and the difficulties they caused in both professional and social settings (although it is likely some of his close friends were already aware of the problems). The cause of his deafness is unknown, but has variously been attributed to typhus, auto-immune disorders (such as systemic lupus erythematosus), and even his habit of immersing his head in cold water to stay awake.The explanation from his autopsy was that he had a “distended inner ear”, which developed lesions over time. Paget’s disease is another possible cause of his deafness.

After Beethoven went deaf, he found he could affix a metal rod to his piano and bite down on it while he played, enabling him to hear perfectly through vibrations in his jawbone. The process is called bone conduction.

Bone conduction is the conduction of sound to the inner ear through the bones of the skull.
Bone conduction transmission can be used with individuals with normal or impaired hearing. Bone conduction is one reason why a person’s voice sounds different to them when it is recorded and played back. Because the skull conducts lower frequencies better than air, people perceive their own voices to be lower and fuller than others do, and a recording of one’s own voice frequently sounds higher than one expects it to sound. Musicians may use bone conduction while tuning stringed instruments to a tuning fork. After the fork starts vibrating, placing it in the mouth with the stem between the back teeth ensures that one continues to hear the note via bone conduction, and both hands are free to do the tuning.
Some hearing aids employ bone conduction, achieving an effect equivalent to hearing directly by means of the ears. A headset is ergonomically positioned on the temple and cheek and the electromechanical transducer, which converts electric signals into mechanical vibrations, sends sound to the internal ear through the cranial bones. Likewise, a microphone can be used to record spoken sounds via bone conduction.

Bone conduction has rapidly become a critical asset for treatment of hearing loss. While a new generation of cochlear implants has had spectacular success in recent years, they rely on air conduction and the patient possessing a functional pathway from outer to inner ear. For patients with severely damaged pathways, such implants offer no solution.