When spectating an entity (inside of their first person vision), the spectator's scope of sound does not move from where they originally started spectating that entity.

To reproduce:

Log two players into the same world, and set one of their gamemodes to spectator.

Teleport the spectator to the other player and spectate their first person vision.

Move the player being spectated to a far away position, and you will notice that the spectator's position of hearing has not moved with the player.