Beethoven began losing his hearing in his mid-20s, after already building a reputation as a musician and composer. The cause of his deafness remains a mystery, though modern analysis of his DNA revealed health issues including large amounts of lead in his system. At the time, people ate with lead plates—they just didn't know back then.
Continuing to compose and conduct, he changed lodgings（住处）constantly in Vienna, which could be due to Beethoven's neighbors' complaint about his pounding（反复击打）on his piano at all hours.
Beethoven even continued performing publicly as a musician, which was necessary for many composers of the age. That's how they got their pieces out, not just composing but performing. For the longest time he didn't want to disclose his deafness because he believed that it would ruin his career.
Once his hearing was fully gone by age 45, Beethoven retreated from public life. Giving up performing and public appearances, he allowed only select friends to visit him, communicating through written conversations in notebooks. His deafness forced him to become a very private, insular（孤立的）person over the course of time.
A common question is how Beethoven continued composing without his hearing, but this likely wasn't too difficult. Music is a language, with rules. Knowing the rules of how music is made, he could sit at his desk and compose a piece of music without hearing it. Beethoven's style changed, however, as he lost his public life. His once-cheerful musical style began to take on a dark tone. His famous Sixth Symphony also reflects his different life in deafness.
