With drastically improved storage and better music playing software, your PDA or smartphone isn't just a business companion anymore; it's also a mini entertainment center. So if you're going to get serious about listening to tunes (or even video) on your handheld, you may want to invest in better headphones, as the pair bundled with most mobile devices are far less than satisfactory.

And if you're a frequent business traveler, you'll want those headphones to cancel out background noise. After all, that loud and constant engine drone on an airplane accounts for much of the stress you feel after a flight. Noise-canceling headphones don't just improve your audio experience; they can also help to make you feel better rested and relaxed.

Before you buy the first pair of noise-canceling headphones you see at an airport kiosk, read our roundup of all the major players. We found that there's a range of prices and styles, and that some block noise far better than others.

Bose QuietComfort 2
Mention noise-canceling headphones and many people automatically think Bose. We're happy to say the company lives up to it's reputation with the QuietComfort 2.

You'll first notice the luxuriously soft cushioning on the ear covers, and that the covers fit all the way around the ear, never on top of it. They fit snuggly against the head, providing a fair amount of noise blocking even when the headphones aren't switched on.

The QuietComfort 2 is one of only two pairs here (the other being the Macally PodPro) that let you detach the cord from the headphones and still use noise cancellation, so that you can use them to block sound while working around loud machinery or while sleeping on a plane.

They come with a hard case with a carrying strap, a stereo mini plug adapter, and a two-prong airplane adapter. The only thing missing is a monitor button, like the Sony has, to better hear announcements.

In testing, the Bose outperformed the others here, easily providing the best noise cancellation of the bunch. No headphones block out every sound, but the Bose did an excellent job of blocking out enough so that we could listen to music without distraction.

The only hitch is that they won't work as standard headphones without a battery, so be sure you have a spare on hand (they take one AAA). The price is certainly high ($299 list), but if you can afford it, we don't think you'll be disappointed.

Creative Headphones HN-505
The Creative noise-canceling headphones offer good value for not much money. While they're not as comfortable as the higher-priced models and don't have the same frequency range, they still do a fine job of blocking out external noise.

Since the ear cushions aren't as large as those on the Sony or Panasonic, they don't fit all the way around the ear but rather rest of top of it. This can be uncomfortable when worn for a long period (like, say, on a plane), so you'll want to take them off now and then. They come with an airplane adapter and a drawstring carrying case.

We were happy with the Creative's performance, which was great for a low-priced ($49.99) model. When switched on, they did a solid job of blocking out background noise. They can be used without noise-canceling turned on, although they'll make your music sound a little flat then. Turn on the noise-canceling, even if you don't need it, for a much fuller and more dynamic sound.

Macally PodPro Noise Reduction Headphones
Like the Creative headphones, the Macally are a great choice for bargain-hunters, proving that you don't need to spend a fortune for good-quality noise-reduction. The two are awfully similar, but we give the edge to Macally, which produces a sharper sound.

Macally's PodPro comes in iPod white and lists for $69.99. The ear cushions are slightly larger than the Creative's, so they feel a little better in use but can still be uncomfortable for extended wear. However, they share one design advantage with the Bose QuietComfort 2: the cord can be detached from the headphones.

That means you can use the noise-reduction feature unencumbered by a cord when not listening to music. It's a great way to get some sleep on an airplane. They comes with an airplane stereo adapter and a zippered case, and run off two AAA batteries.

Like the Creative headphones, the Macally can be used without noise-reduction turned on, but the sound is flatter and muddier. Better to always have it switched on. The noise-reduction is quite good for low-priced headphones, and they'll block out much of the external noise around you. They don't have the same dynamic range as the Panasonic or the Sony, but sounded slightly better than the low-priced Creatives in our testing.

Maxell HP/NC-II
Like the Macally and Creative models, the Maxell headphones are for budget shoppers (they list for $49), but they don't provide as much noise cancellation as others in the same price range.

Surprisingly lightweight, the Maxells fit comfortably around the ear and offer some cushioning, although not as much as the higher-priced Sony. The on/off switch is on a plastic compartment in the middle of the cord that also houses the two AAA batteries. The packages comes with a drawstring bag and an airplane adapter.

The Maxell isn't a strong performer, though, as it didn't reduce background noise well in our testing. The Macally and Creative models did a much better job for about the same money. Even worse, though, was how it flattened out the music when noise-reduction was on. It stripped the music of much of its dynamic range and left a sound more akin to AM radio.

Panasonic RP-HC300
Panasonic's noise-canceling headphones sell for the same price as the Sony ($199 list), but deliver less for the money: The headphones don't feel quite as sturdy or well-made.

They come with stereo mini-plug and airplane adapters, although neither is gold-plated, like the Sony's are. The only control is the on/off switch. And there are no controls to adjust the volume or noise-reduction levels, and there's no monitor switch. The ear pieces are well-cushioned, though, and fit comfortably around the ears. The Panasonics also come with a sturdy, hard zippered case.

We were a little disappointed by the Panasonic in use, since it plays music with a flat, echo-y sound. Most of the other entrants produced a richer sound. We were also surprised that it won't play music unless it's switched on; all of the others will work as standard headphones when powered off or when the batteries are drained. It reduces outside noise by a fair amount, although not as much as the Sony. Outside sounds were still clearly audible.

Philips HN060 Noise-Canceling Headphones
These Philips headphones are one of the less-expensive pairs we looked at (the list price is $59.99). They were certainly the least satisfying pair.

The headphones use an in-ear design, like the Shure headphones, but don't come with different removable end covers, so that you're stuck using the large ones attached. They felt uncomfortable during use, wedged into our ear canals. Unlike the Shure, the Philips don't come with a pick tool to remove the earwax that will accumulate during use.

There's also an unusual cord that wraps around the back of the neck in order to support the batter compartment (it uses one AAA battery), which hangs at about chest level. This makes them unusable for athletes, since the battery compartment would bang around while running or biking. They come with a small carry pouch, an airline stereo adapter, and a stereo mini plug adapter.

As much as we didn't like the physical design, the performance was even worse. When switched on, the Philips didn't seems to block outside noise in the slightest, but only to increase the music volume so that we could hear it better. We gave them several chances, but they never canceled the level of outside sounds at all.

Sennheiser PXC 300
Sennheiser's noise-canceling headphones have a unique shape unlike the others in this roundup. Rather than either the large ear covers or the in-ear designs that we see from other companies, the Sennheisers have a lightweight over-ear design that's perfect for people who are bothered by heavy headphones.

They're not much larger than headphones that would come free with a compact CD player, and they fold up small when not in use. Small cushioned ear covers offer comfort and don't become irritating when worn for long periods.

The headphones run off two AAA batteries which ride in a plastic shell halfway down the cord. This makes the headphones lighter, but does require you to clip the battery compartment to your pocket or belt. We prefer batteries to be inside the headphones themselves, for less hassle, but it's a matter of personal taste. The Sennheisers come with a hard zippered case, an airline stereo adapter, and a stereo mini plug adapter.

The Sennheisers did a fair job of canceling background noise, but not as good as we would have liked for a high-priced model (they list for $219.95). Even the lower-prices Macally and Creative models did a better job. They produced a rich stereo sound and even work as headphones when switched off (or when the batteries are drained), although the sound reproduction isn't quite as good then.

Shure E4c
Unlike other products here, Shure's earphones don't work by actively countering external sounds; rather, they simply block them. The E4c fits snuggly in the ear canal, preventing external sounds from coming in.

To help you get a good fit, they come with eight different earphone sleeves-which fit around the earphone and make contact with your ear canal-so that you can choose the one you prefer most. You'll get three sizes of flexible PVC sleeves, three sizes of more rounded flexible rubber sleeves, one set of foam sleeves (which compress and expand like foam earplugs), and one set of triple-flange sleeves, which give three levels of sound prevention.

For the best fit, the Shure cord needs to wrap up and behind the ear, which along with the in-ear design, can be hard to get used to. The earphones also come with a "level attenuator," which you can use to adjust audio from loud sources, a cleaning pick for removing the earwax that accumulates in the earphones, a gold-plated miniplug adapter, and a small carrying case. Unfortunately, they don't come with an in-flight adapter.

The E4c's in-ear design is uncomfortable at first, but the earphones do just as good a job at blocking noise as the larger headphones we looked at and are far more portable. They also reproduce music extremely well, producing a rich, full sound. While the price ($299) is high, their audio quality and portability will certainly find a lot of takers.

Sony MDR-NC50
Sony's noise canceling headphones deliver executive-level perks at a reasonable price ($199 list). We first noticed how luxurious and well-made they felt, with large cushioned ear pieces that fit around the ear, rather than resting on top of them, for an extremely comfortable fit.

They work off one AAA battery and have a useful monitor switch—which you can press to temporarily hear what's going on around you, rather than your music—that we didn't see in any of the other models in this roundup. There are no volume controls or noise-reduction controls, unfortunately. The package includes a gold-plated stereo mini-plug adapter, a gold-plated in-flight adapter (one prong can fold down for single-prong systems), and a zippered carrying case.

In use, the Sony provides excellent stereo sound, although it reduces outside noise slightly less than we would have expected from such a well-designed set. Outside noise is still present, though it's reduced enough so that you can easily ignore it.

Executive Summary
The Macally PodPro is a good buy for bargain shoppers, but for real executive comfort, try the Bose QuietComfort 2 or the Sony MDR-NC50.