Well.. I did turn the head as you suggest and I hear the hub cannon with the head turned. But this is something new....not to be able to hear it looking straight forward.
I've always been able to hear them before.... and my squaddies say they can hear the hubs fine....
Your wearing headphones?
If your wearing headphones go to desktop and select your sound and set your speakers to HEADPHONES!
If your sound setting are set to 5.1 or something such then your HEADPHONES will not give you FULL surround sound so you will not hear somethings!
Had the same issue and tinkered for awhile then it HIT me!
Surround sound does NOT work with HEADPHONES!
Unless you have (EXPENSIVE?) SURROUND sound type headphones!
Pretty sure if you change your setting to HEADPHONES, and your using them, you will get FULL SOUND, including nose cannon sounds!