I used to commute to work on the train. It was a 40 minute ride and I would always grab a seat in the car nearest the engine because it was closest to the station exit I took at my destination. The problem was the rumbling noise from the engine.
I tried noise canceling headphones, but I seem to be sensitive to (at least the old) noise canceling technologies. I would get nauseous and disoriented. I didn't like the idea of closed back headphones because they were so bulky, and as I mentioned in my A900Z review, I never had issues with open backs in the office. My solution, then, was to try headphones that went deep into my ear. Sometimes these are called in-ear monitors (IEMs) and sometimes they're called earphones.
At first I tried some very cheap IEMs I got off Drop.com (then Massdrop). They broke in less than 2 months. The day they broke, I happened to see a sale on the Etymotic ER3-XR. Etymotic is a brand well-regarded for their sound quality and noise isolation, but they were normally more expensive than I was willing to put up with. On sale at 50% off, I sprung for them.
Noise cancellation
The reason I got these earphones was to cancel out noise while I was on the train. While I no longer take the train very often, I do fly on airplanes regularly and work in an office once a week or so. Sound quality was always secondary to the noise isolation they provide.
The Etymotic style of silicon ear tip is the best noise isolation I have ever experienced.
No questions about it, these earphones have the best noise isolation I've ever experienced. They are on par with some of the active noise canceling headphones I've tried in the past. When I properly insert these into my brain (yes, they are invasive, more on that later), I can barely hear anything else going on around me. I've used them to drown out jackhammers in construction sites next door and babies on planes, and they've delivered every time. I've seen some threads online of folks claiming that the 3 flange silicon tips, properly inserted, qualify as sound protection equipment on construction sites.
The best part is that you can't lose the seal halfway through the day. Over-ear headphones move around on your head. Turn your head too fast, and they lose the seal. Wear glasses with thick enough frames and you lose the seal. These things go deep into your ear, so while they might slowly shake loose as you jiggle around, they'll always provide pretty darn good isolation.
The issue, though...
You gotta go deep (comfort)
These things insert deep into your ear. Extremely deep. So deep, I call them my "brain ticklers."
Some people will hate how deep these have to go into your ear. It's certainly an experience inserting them into your ear. I have to pull my ear back a bit to prevent the eartips from compressing air into my ear canal on insertion, and if I ever pull them out too fast (like if I swat the cable by accident), I can feel the negative pressure pulling my eardrum.
All that being said, at rest these are incredible comfortable. They're crazy light, so light that they don't have to hook around your ear for support like some in-ear monitors do. If you get the correct eartip size and insertion level (unfortunately there's some trial and error here), they're perfectly snug inside your ear and the center of gravity doesn't feel like it's pulling them out of your ears. I've occassionally forgotten that I even have them in.
The problem is that, on long days with the ER3-XRs inserted into my skull, the skin in my ear canal gets sore. Even though they don't pop out, they do move around a bit as you move around, and the inside of your ear is (generally) not very used to any kind of friction. Eating in particular is a problem. Your ear canal will change shape as you chew, causing all kinds of movement and leading to an annoyingly painful ear.
The foam tips solve some of the issues with friction and pressure changes in your ear canal, but I've found that they will slowly wiggle themselves out of my ear of the course of a long flight. They also aren't meant to be used too many times, as the foam will start to compress and lose some of the properties that make it such an excellent absorber of noise.
This is particularly true on overnight flights, where I put the ER3s in my ears as soon as I get into my seat and generally don't take them out till it's time to get off the plane. Over those 6 or so hours, I'll shift in my seat, eat, and drink water, all of which can pull on the cable or otherwise cause shifts. Combined with wearing a mask, my ears are often raw by the time I get to my destination.
Sound
It can be hard to separate insertion quality from sound quality with Etymotic earphones. If you don't insert deep enough, the bass response will not behave as expected. Improperly inserted, the earphones are sibillant and lacking any resolution in the lower frequencies. When you do insert them correctly, the ER3-XR are fantastic sounding earphones.
As the frequency response shows, these are incredibly neutral-sounding earphones. Etymotic tunes all their models to be their version of "neutral" at correct insertion depth. The dark line on the graph is a definition of neutral that Crinacle uses for his graphs, and you can see the ER3-SE has slightly less bass and a closer adherance to that version of neutral:
This is where it makes sense to bring up an important distinction: the XR suffix of the model names stands for "extended response", while SE stands for "standard editiion". The extended response versions of Etymotic earphones tend to have a fair bit more bass (2-3 dB or so) but keep the same general response shape. It's one of the most tasteful versions of bass I've ever heard; not too much that it becomes a bass-forward response, but just enough that you notice it.
It's hard to describe how easygoing and natural the ER3-XRs are. No part of the frequency range jumps out. You never feel bass hits like you can on some headphones, but it's clear the bass is slightly elevated and well balanced. You don't get any shrill tones or sibilance from the highs, but the detail retrieval is exceptional. I'm consistently blown away by the quality of sound coming out of these earphones when I get the chance to listen to them in a quiet environment.
The cable
I don't really like the stock cable on Etymotic earphones. It's not hard to replace, but I just haven't put in the effort to find one that didn't cost snake oil money.
The cable is loud. When you touch and rub the cable, you can hear it through your music. It's not microphonic, but extremely sensitive to any contact that might be made with it.
It's also a bit too short for a cable attached to earphones you're expected to travel with. 5 feet is my preferred length, but the cable is only 4 feet long. I will regularly hit the cable gently as I'm moving around, and it's short enough that it will always pull on my ears because there isn't enough slack available. As mentioned, when you have inserted any Etymotic earphone properly, pulling them out can cause a vacuum to build in your ear canal if you're not careful. I regularly have painful moments where the cable gets caught on something (usually one of my flailing limbs) and pulls on my eardrum.
Value
I don't think the ER3XR are worth it. Even though you can find them on sale for around $100 nowadays, the existence of the ER2 models basically nullify the need to pay any more than $70 or $80. The only difference between models is the type of driver inside the unit, but all Etymotic models are also tuned to be extremely similarly tuned.
Given you're most likely to be in a noisy, on the go environment when wearing in-ear monitors, it doesn't make sense to me to pay extra money for the ER3 series, which promise a bit more resolution. I've had the opportunity to try the ER2 standard model, and while it has less bass than my extended response model, I saw no reason to pay more money for the upgrade. The resolution, timbre, and tonal balance is exceptional even at the bottom of the Etymotic line, and it's just not possible to recommend spending more money.
Verdict
If you can handle the insertion depth and the slightly noisy cable, the Etymotic line of earphones are exceptional. The sound quality they deliver is mind blowing for how tiny of a package they come in, and the noise isolation they provide makes any room a quiet room. I cannot recommend the ER3 line because of the price jump from the ER2s, but I can still wholeheartedly recommend Etymotic earphones for sound quality and noise isolation.