A good seal is of the utmost importance for excellent sound quality. When the seal is not right, the bigger part of your bass tones will leak away. The mid and higher tones will gain the upper hand, which will induce the sound quality to be absolutely bad. It is almost impossible to have a good seal right away. You’ll need to experiment for a while and to get used to plugging in your IEM. That might cause you to feel disappointed in your new gear. Please, persevere and try different kinds of sleeves till you have reached the perfect seal and fit.
How to reach the perfect fit.

It is very hard to give a general advice on reaching the perfect fit, because every ear is different. For rubber sleeves like the triple flange I would advise you to use  the lick and stick principle. Moisten the sleeves with some saliva before plugging in the IEMs. By doing so, it is easier to plug them into your auditory canal. The best way is to pull the upper side of your auricle up (over your head) to widen your auditory canal. Then you use your other hand to plug in the IEM. It might be useful to realize that the canal is not vertical but slanting. Don’t be afraid of pushing them in too far; the shape of the IEMs makes that impossible.

You’ll never be able to block out all the surrounding noise . Once you’ve reached a good seal, however, you won’t hear anything but music. A general advice I would like to give you is to experiment and to not give up. Once you’ve got the hang of it, plugging in and sealing will take you just a couple of seconds. Practice makes perfect!