You can adjust but there are consequences...
I have my internal sounds turned WAY down (to 15 I believe). I have my outside sounds turned up (somewhere between 65 to 80). Basically, I can hear an approaching plane from about 1.2 to 1.5 out when I am in my plane.
The consequence to that is you hear friendly planes loud when in tight formations.
Just find that balance that you can live with.
Should be in the advanced settings. I am going off memory though.