Sound editors annoy me with this habit of making almost all helicopters on film sound like a two-bladed Huey but they are just sound editors, not a helicopter nut like me.
More lately I've noticed they tend to edit together the sound of different machines depending on what the helicopter is doing. Eg. approaching from a distance = Huey. Fast fly by = Gazelle. Landing = Bell 407 or similar four-blader.
A lot of credit must be given to the sound editors on Blue Thunder who kept everything consistent between the three main featured helicopter types. Even when the JetRanger formates with the Gazelle during the "flight check" scene, you can hear on a good sound system that they put a lot of effort into getting it right.