I'll reinforce this. It should NOT be possible to turn down your own engine to be able to hear other aircraft approaching more easily.
Listening to the engine of other planes behind you reminds me of that sticker on the side mirrors or cars, "objects are closer than they appear". I understand what you are saying about people lowering their sounds, I had mine really low, but not to listen to other engines, it was so just because the sound of my engine was driving me nuts.
As for Cal's posting a big +1. that and get rid of the air raid sound, I replaced mine yesterday with the pigs's authorized check six sound and it drove me nuts in about 40 seconds (sound is a pig squealing, lol). now I replaced it with a blank sound.
semp