this is not entirely true, see the movies here shows Kadimbey Daniel F juls2008 , new buses that we have in the game like MAN LION COACH, Neoplan, Setra all bus each sound definitely louder and have these sounds different, you can hear the engine, gears, brakes, which is why TML STUDIOS is to change the program to the sound of the game, the sounds of buses are to be recorded live and added to the game, which I write here Quarney
Yes you are right. Unless buses have an electric motor, it is natural for them to have motor sound. You hear all kinds of engine sounds because they have a very powerful engine. I had the chance to board many buses in the game as passengers. I got on the Mercedes buses the most, but they also have engine noise. I never got on the VDL bus.