Are sound waves characterized by crest and troughs?

They can be.

In air and other fluids sound is transmitted by variations in pressure. When those variations impinge on the eardrums (in our ears) they make them vibrate. If we were able to monitor the horizontal position of a point on one eardrum through time (assuming that the person in possession of the eardrum was standing) then we would see a complicated wave form with crests and troughs.