A Db-meter probably won't help you much, because that only gives you a general level, not tell you that a sound is going to annoy you. only ears can do that, and its much more a function of frequency over volume. there are heaps of free frequency analyzer apps that run off a smart-phone, those will let you know if you have a spike in a certain range. But realistically, that isn't going to tell you all that much, unless you are going to start engineering your space.
If you want just a generally quieter house, look at heavy curtains, or honey-comb style blinds, they have the additional advantage of also allowing you to let light in the top, but block the bottom of the window. Anything on your walls that helps break down echos, especially large walls, or opposite windows. Glassed picture frames reflect a lot of sound, so having them 90deg to the window helps, but only by a small amount in a large room, hardly at all in a small one. carpet or throw rugs, to attenuate the floor, and insulated ceiling spaces. Think about it less of blocking out the sound, but more killing the waves as fast as possible. A lot of ambient noise is just echos rattling around.
Doors are another good thought, although if you already have solid core doors, you may not gain much. Acoustic doors are generally for internal use, and to be honest, they are often not worth the wall they are installed on.
I think a really good start will be those single-pane windows. Doubles, or triples will also really help with your climate control and bills. Personally I think you'll over-pay if you are trying to go for some special sound resistant design, but just well built, sealed windows will be nearly as good, for much cheaper.
Is your attic/upper crawl space insulated? adding some insulation up there will attenuate some of the aircraft noise, but not all, since the lower frequencies will ruble through regardless, but by cutting out the high frequencies, you also lower the overall power.
So basically anything you can do to make your house more energy efficient, will also make it quieter. There are a lot of products out there for deadening sound, and to be honest, the vast majority are marketing hype. They may well work, but not because they are special. Most insulation types will give you a sound attenuation rating as well as the R-value, softer insulation attenuates better than hard block, but even block foam will be better than timber or tin. Depending on the construction of your home, your walls may be as big a culprit as your windows. what sort of insulation is there?
