If suddenly sounds became lethal, I think it would be dangerous more than changing everyday life. Something as simple as birdsong or a sigh would be something to avoid at all costs. Happiness would leave our lives, as a smile without its characteristic sound is not a smile, it is just a facial expression. I would miss music a lot, the sound of the wind, the voices of my loved ones, and the barking of my puppy.
Communicating would be almost impossible for some people, as although sign language may be useful during the day, at night it would not be as effective over long distances. An alternative would be to use the light language that sailors used. I think it's like Morse code, but turning lights on and off. Here arises another problem, as blind people would be unable to communicate.
But it would not only affect the lives of individuals, but also at the level of communities and countries. I can't imagine a construction site or a factory completely silent, so I take for granted that technological progress would be completely halted. Even going from one place to another would be complex, as we should forget about conventional means of transportation, since even walking produces sound depending on the terrain.
If sound became lethal and we managed to survive the danger it brings, I think we would devolve in such a way that we would lose many traits that currently define human beings as a species.