Yes the default engine sounds in AH are all the same. AH's default installation is rather sparse with regards to sounds and this is pobably one of the game's biggest weaknesses. Sounds are every bit as important for immersion in a "simulation" as the flight model is!
Fortunately this can be rectified with 3rd-paty sound packs. One such self-installing sound pack is "Mitsu's sound pack" ; you can find links to download it on this forum. While such sound packs are seldom of the quality of something produced in-house, it is certainly an improvement over the current default install.
J_A_B