Excerpt: I did my homework when I decided to purchase this product, and I am very satisfied with this pair of headphones. The sound cancelling feature works very well, and the sound quality is wonderful (I don't find any specific boost in bass or treble, but it is a delight to listen music with). I am a frequent flyer, and having a pair of noise canceling headphones to take out the plane engine noise makes my flight more musically enjoyable.
Summary: Only thing that could use a bit of a boost is the low end. Its not as forceful as others, but still incredibly well represented.
Pros: The noise isolation is fantastic. I do believe they could double as hearing protection. I put them in at work and it blocks out everything except for the piercing phone ring I turned up a foot away from me.
Conclusion: I own lots of Klipsch audio products, and the Reference S4i In-ear headphones are excellent! They deliver crisp, clear detail. Well rounded highs, mids and lows that the reference series are known for. They look nice and the controls on the cable are very functional. The Reference S4i's are well worth the purchase!
Conclusion: Good sound, the cord doesn't get tangled, and they stay in ear really well. What's not to like? The only issue I had is that the built-in controls don't work for some older devices, but as long as you check compatibility first you should be fine.
Conclusion: Since purchasing i have found other Sony headphones that give better sound quality and lasted longer. These things pop out of your ear too quickly. Don't run with these. The "tangle free cable" is tangle free, but it sticks to clothing way too easily. Sticks to almost everything actually. It doesn't stop sound like it says, it only isolates it slightly. No in ear headphones can stop sound from coming in from the outside world. Worst headphone I have ever owned.
Conclusion: These headphone definitely block outside noise and are comfortable to wear and have good sound quality. The only thing I do not like is when I'm wearing them while exercising any movement of the cord is amplified in the ear buds. For that reason alone I would not likely spend the money to purchase this item again.