I am glad you have enjoyed it so far. Sound does become somewhat more important over time, particularly in Episode 11 (where my work begins). I would say most of it can be enjoyed without audio, but there are some audio enhanced jokes you will not be able to fully appreciate without sound (but it still is largely script driven). I am curious as to the cause of your lack of sound.
One more thing, is that an image from the part of CTU where Crono is searching for a way to save Frog's life?