Trust me (or turn on the subtitles), it's there.
Speaking of saber sounds, I agree, that ROTJ's are hardcore. Since it was the SW movie I saw first and the one I saw most often, I've always assumed that's how sabers are "supposed" to sound like. They sound powerful! Now compare that to ROTS. Unless you really boost the base, they don't sound nearly as cool (it's like the people are just lightly swinging them at each other). Especially compare when they clash...