Additional sounds are a bit of a nightmare for me, especially loud music, my brain cannot separate from the higher volume to concentrate on a conversation, i have noticed most people are able to separate these sounds and was always a mystery to me as to why i couldn't, i have to move away from the main source for my brain to be able to take input of individual in.. An example is being in a pub with music ( rarely go to those places now) and i will have someone trying to talk to me, and i shrug my shoulders and say sorry i cant hear, so they will be close to my ear and talking loudly, however my brain is still focused on said music and for most would be able to hear that person but for me i still cant... However i sometimes get this in normal conversation also without any other external distraction, its a bit weird, but its like i am hearing everything they are saying but my brain just isnt registering, and by the fifth time i have asked them to repeat, suddenly as they are mid paragraph, my brain decides to register what had been repeated earlier!... I used to get in a lot of misunderstandings with this, especially in louder places, as i would just smile and nod my head, as people seem to get frustrated if they have to repeat themselves more than twice, so i would just smile and nod, to find out im nodding to something i shouldn't, seems this is another area gross misunderstandings can take place 
Also when at school, i was never one that could have headphones on and do homework at the same time.. Again one sound source at a time for me...
I have also noticed when i get brain delays it seems to come from people with similar vocal frequencies, so wandering if variants in sound frequency can also effect brain input?