These are little foam plugs. You roll them in your fingers so that they become thin, insert them in your ears and they expand blocking out some, but not all of the sound around you.
They block out much but not all of the high and mid range frequencies of sound, and don't do much for the low frequencies. The very low frequencies are more felt than heard anyway.
I use the Hearos earplugs ($2 a pack) because they are flesh tone and less noticeable. When I travel I just carry a pair in my pocket and casually pop them in when I need them. There are times I'll just pop one in one ear. Anything to help filter out found that is becoming overwhelming.
I spoke with a coworker that purchased sound isolating headphones. For a $100 plus a pair, make sure that you really do your homework and don't just take Dr. Bose word for it. Apparently the BOSE headphones really block out sound and surround the ear nicely.
The question is when you travel do you need something to completely isolate all sound (if possible) or just to cut back. The foam earplugs block out sound, but I can still hear what people are saying, and even speak. Speaking is something of a challenge, because I can't be sure how loud I am. Turns out that when I have them in I talk more quietly.
Frankly, when I travel, even if things aren't loud, they and the sun glasses cut back on the amount of data to sort in my brain, and I often just leave them in the whole time I travel.
I do NOT recommend wearing them if you are driving the car. You need to be able to hear everything in order to drive a car safely.