I think that if a person is noticing things that are happening around, then they are not focused on what the person they are conversing with is saying. That is not good when you are on a date. You should be focused exclusively on what the person is saying, as you might miss something important. That person deserves your undivided attention. Let the background noise fade and pay close attention to what this person is telling you. I think this applies to all conversations, giving 100% attention to the other person, I mean, but so much more so in a shidduch.
Personally, I find that if I’m talking to someone and they are doing something else at the same time (it could be simply looking around – eye contact is a very important way to communicate that you’re paying attention), I feel rejected, as if the other person does not care to talk to me, so I just abandon the “conversation” at that point most of the time, but this is just me.