So most of you probably own at least one iPod, Zune, or other MP3/PMP player. These devices usually cost several hundred dollars and apparently based on the iPod’s monumental success, millions of people are happy to pay for them. When it comes to the most crucial part of the sound reproduction chain, the earbuds, few people actually invest in a good pair. Aside from sound quality benefits, I contend that there is also an invaluable reason for buying some good in-ear-monitors: they can save your hearing.

Multitudes of people who listen heavily to MP3 players are losing their hearing. My antidote to this problem is the IEM because they isolate you from outside noise. Generally, the attenuation provided by a good IEM is around -10db or more. This means that you can listen at 10db lower than with an earbud that gives no isolation. Musicians have been using IEMs from Shure, Ultimate Ears, etc. for years.

Choosing an IEM is actually not too difficult because there are only a handful of choices. Since most consumers will not be able to test an IEM (for sanitary reasons) before purchasing, they should read all of the reviews and do extensive research before buying. From my experience, most of the major manufacturers covered here make technically solid products in their respective price segments. Your tastes in music and sound should determine which model you select. The frequency response charts included are courtesy of headphone.com. Please refer to the charts for a general idea of what the IEMs sound like. Remember that every ear is different, so technical data alone does not always indicate what an IEM will sound like to you.

Sennheiser CX 300 $59.99: this is a favorite among listeners on a budget. It is a clear step up from many earbuds that are bundled with MP3 players. I think that these little guys are suitable for any genre of music, but they do tend to be a bit “warm,” so heavy metal and hard rock might seem less aggressive than with other monitors. One significant problem that I have with these is that they attenuate only -8db. Consider also Sennheiser’s $99.99 model, the CX 380.

Etymotic ER-6i $149.99: OK, so these are technically more than $100, but they can be had for well under that from most vendors, so I am including them here. These were my first “good” IEMs, and I would definitely recommend them to everyone except bassheads. The chart shows that the bass is actually flat with the mids, but even when properly sealed in your ears, these IEMs still sound slightly rolled off at the bottom end, with little impact below 100Hz. For rock, alternative, and pop though, the ER-6i is fairly detailed and more than copacetic. Isolation is -20db.

Shure SE110 $119.99: Amazon sells these for under $80. To my ears, the SE110 sounds like a slightly more refined CX 300, with a bit more resolution and clearer mids-highs. Heavy rockers should be aware that the general Shure sound is warm and a bit mellow at the top-end, while lightly emphasizing mid-bass and lower mids. Isolation is around -20db depending on which tips are used.

Ultimate Ears SuperFi 4 $129.99: On sale at Amazon for $64.99 after rebate, these are quite a bargain right now. I do not have their frequency response chart, but the SuperFi 4 falls somewhere in between the ER-6i and CX 300/SE110. Perhaps the Ultimate Ears can be regarded as the best Jack of All Trades IEMs. Isolation is also an excellent -26db. I think that these look the snazziest too.

There are many other options out there, but these four candidates are the most established and well regarded IEMs under $100. Next, I will be looking at sub-$200 cans from Westone and other manufacturers.