The earliest evidence for his hearing loss was in 1798. In an 1801 letter, Beethoven wrote to his friend and physician Franz Gerhard Wegeler that he had become weaker during the past three years.

Beethoven also complained not just of hearing loss, but sharp pain, ringing, and chronic earaches. But he was not completely deaf during these early years.

So Beethoven probably could hear a number of sounds, but it was within a very limited range and got worse over time. However, his letters also attest to the fact his hearing loss also caused a great deal of physical pain and discomfort.

Edit: made a stupid mistake here, quoting the wrong letter Source

Lockwood, Lewis. Beethoven: The Music and the Life. New York: W.W. Norton, 2005