The Prequel References in The Force Awakens
You may have heard the voices of Alec Guinness, Ewan McGregor and Yoda in Rey's vision but what you didn't hear was the sounds of the prequel trilogy in the back of your mind. There were several callbacks in The Force Awakens to the original trilogy but the only references to the prequels were merely sound effects, peppered throughout the movie, only noticeable by the eagle-eared viewer.
For example, when Finn and Poe are shot down in their TIE fighter, there's a brief sound of a missile, reminiscent of Episode II during the beginning of the Clone Wars.
When Han Solo, Chewbacca and Finn gain the upper hand on Captain Phasma and make her lower the Starkiller Base's shields, you hear a quick sound you once heard in the interior of a Naboo Starship
After Kylo Ren shoves his lightsaber through his father, Han Solo, there is a brief sound from when Obi-Wan struck Darth Maul through the chest:
Lastly, at the end of the film, when Rey is saying goodbye to Finn, the heartbeat that is heard, monitoring him is heard in Episode III, at the Polis Massa delivery room, right before Luke and Leia are born.
Besides the star chart in the Millennium Falcon, half-way through the film the only references to the prequel triology were auditory. It was as if JJ Abrams wanted to remind you that the technology from the prequels still exists and that's it