At what age did the composer Beethoven lose his hearing and what symphony was he working on?

Around the age of 26, Beethoven began to hear buzzing and ringing in his ears. In 1800, aged 30, he wrote from Vienna to a childhood friend - by then working as a doctor in Bonn - saying that he had been suffering for some time: "For the last three years my hearing has grown steadily weaker.

Beethoven was 31, and was working on symphony no. 2