Wireless cellphone earpieces can make people look faintly ridiculous as they stroll down the street or around the office, seemingly talking to themselves with ugly appendages sprouting from their heads. The pulsing blue lights on these things can make people look like robots. And these battery-powered gadgets, which use a power-hungry wireless technology called Bluetooth, are just one more thing to charge.

But such headsets are becoming more necessary, at least in the car. A growing number of cities and states are requiring all calls made while driving be conducted in a “hands-free” manner. Two more big states, California and Washington, will begin enforcing such laws in July. Unless drivers in these places have cars with costly built-in Bluetooth speakers and microphones, many will turn to wireless earpieces to make calls legally.

Now, two of the most important wireless earpiece makers are bringing out new models that attempt to make their products more attractive and functional. One is a new version of the Jawbone, which has become a leader in the high-priced end of the market. The other is a new model from Plantronics (PLT), which vies with Motorola (MOT) as the top seller of wireless earpieces.

I’ve been testing both the new $130 Jawbone, and the $150 Plantronics Discovery 925, and both work well, despite some drawbacks. Each worked properly with both an inexpensive Motorola Razr phone from Verizon (VZ) and a sophisticated Apple (AAPL) iPhone from AT&T (T). But I preferred the Jawbone, because of its technology and design.

The new Jawbone, made by a closely held San Francisco company called Aliph, is 50% smaller than the original Jawbone, which I reviewed in 2006. It continues to boast the original Jawbone’s signature feature: a remarkable ability to suppress background noise and isolate the wearer’s voice.

Jawbone performs this feat by using a sensor that touches your skin lightly to identify your voice through the vibration of the bones in your face. Using this information, its microphone can more easily distinguish your voice from background noise, and accurately suppress the latter.

This feature, originally called “Noise Shield” and now theatrically renamed “Noise Assassin,” really works. When the company first showed off the original Jawbone, it made live calls standing in front of things like weed whackers and boom boxes, and then turned the bone-sensing feature on and off to show the dramatic difference.

Aliph’s new Jawbone

In my tests of the new, much smaller Jawbone, I stood a few feet from a roaring vacuum cleaner, while on a phone call. The person I was calling could barely hear me with Noise Assassin turned off, but could clearly make me out when I turned it on.

By contrast, the Plantronics Discovery failed my noise test. It was useless anywhere near the vacuum cleaner. This was obviously an extreme case, but it served as a stand-in for other loud noises likely to be encountered in real life, like large trucks, or construction gear on the streets.

The biggest flaw in the original Jawbone, in my 2006 tests, was its performance in wind, which was poor. The Jawbone did much better in my latest tests. During a Jawbone call from a car with all the windows down and the sunroof open, my voice was easy to make out, according to the person I was calling. The new Plantronics earpiece did just as well in this wind test.

Plantronics claims its headset also enhances the voice of the person you are calling, a claim Aliph doesn’t make for the Jawbone. But, while voices sounded fine on the Plantronics, I couldn’t detect any difference between the two on that score.

Both gadgets are meant to be more stylish, and both will be available in multiple colors. But, while the Jawbone is just a smaller iteration of its original slab-like form, Plantronics has done something more radical with the Discovery 925: It has tried to make it look like jewelry. The Discovery’s electronics are housed in the diamond-shaped portion of the device that goes on the ear, and the microphone sits at the end of a long, V-shaped boom that is open in the center. Plantronics says the design is suitable for both genders, but admits it is a bit more aimed at women and at fashion-conscious men.

I believe some men wouldn’t feel comfortable wearing this new Plantronics model. It’s also longer than the Jawbone. But I did find it more comfortable to wear, since it doesn’t protrude as much into the ear.

The Plantronics claims longer talk time — five hours vs. four hours for the Jawbone, but the Jawbone claims longer standby time — eight days, vs. seven days for the Plantronics. The Jawbone weighs more, at 10 grams, compared with 8 grams for the Plantronics, but neither felt heavy on my ear.

I did prefer the Plantronics’ controls over the Jawbone’s. The former uses obvious buttons, while the latter employs unmarked, hidden buttons whose location you have to learn by touch.

Both of these earpieces do the job, but if you have to choose one, I’d pick the Jawbone.

• Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.

Corrections & Amplifications:

The Aliph Jawbone cellphone earpiece weighs 10 grams, and the Plantronics Discovery 925 earpiece weighs 8 grams. An earlier version of this column erroneously reported the products’ weights in ounces.

But there are problems with going cord-free. In the case of cellphone wireless headsets, loud street and crowd noises make it hard to hear. And the wireless iPod headphones have been big, bulky units of unremarkable audio quality.

Now, some wireless earphones address those problems. For cellphones, a new wireless headset called Jawbone promises to filter out all that background noise. For iPods, new wireless earphones called Ety8 promise to bring small size and great sound quality to the wireless category. Both products use Bluetooth wireless technology to transmit audio from the device to the ear.

I’ve been testing these two new products and have found that each lives up to its claims. Both are advances that have real advantages over the more standard cord-free competitors. But each also has some drawbacks that might deter some folks from using them.

The wireless Jawbone is a sleek, futuristic-looking gadget made by a small San Francisco company called Aliph. It will be sold, starting Dec. 21, for $120 by Cingular Wireless. The earphone will work with any Bluetooth cellphone, not just those on Cingular’s network. Aliph will also sell the new Jawbone on its Web site, www.jawbone.com. The Cingular model will be silver colored. Aliph will offer it in red and black, too.

What makes jawbone special is its noise-cancellation feature, called Noise Shield. You can stand in front of a blaring boom box or a weed whacker with a Jawbone, and its technology, derived from military research, will almost entirely obliterate that background noise. You can also hear the other party better.

This effect is achieved through multiple small, built-in microphones, including one that rests against your cheek, detecting the vibration of your voice through the bones in your face. The gadget uses that reading to help identify and cancel all other sound that isn’t your voice.

In my tests, on a Palm Treo from Verizon and a Samsung Blackjack from Cingular, the Jawbone worked well. On a downtown street, it silenced the sound of traffic and crowd noise. In an office, it blocked out loud music only a few inches away. The noise cancellation is far better than on any other cellphone headset I’ve tried. Battery life is up to a decent six hours.

But there are two downsides to the new Jawbone. First, it can’t defeat wind. Even a mild breeze made Jawbone calls noisy. Second, it has some user-interface problems. The same button that turns the Noise Shield on and off also raises and lowers the volume, and the beeps of the two are hard to distinguish. I also found it hard to get a comfortable fit, though the unit comes with multiple behind-the-ear loops and rubber earbuds.

If you’re an iPod lover, the Ety8 wireless earphones may be just the thing to replace those trademark white earbud cords. Unlike other cordless iPod earphones, the Ety8s aren’t large, over-the-ear headphones. They’re light, in-ear earbuds. They’re made by Etymotic Research of Elk Grove Village, Ill., a high-end audio company whose wired earphones are highly praised.

The Ety8 earphones cost $300 from the company’s site, www.etymotic.com. That includes the headphones and a small adapter that plugs into the iPod to give it wireless capability. You can also use the earphones with other devices with wireless capability built in. For that, you can buy earphones without the adapter for $200.

Like some other high-end earphones, from Etymotic and from competitors like Shure, the Ety8s are meant to go deep into the ear, and come with rubber and foam tips for a snug fit.

The Ety8 also has tiny buttons on the right earpiece to wirelessly control the iPod. You can adjust the volume, play or pause music, or skip ahead or back — all without touching the iPod, which can be 20 or 30 feet away.

They work with the current full-size iPods, the previous generation of full-size iPods, and iPod Nano and Mini models. Battery life is six to nine hours. The adapter draws power from the iPod’s battery, so it will also reduce the battery life of the iPod itself.

In my tests, the Ety8 earphones worked great, both on a new full-size iPod and on an older iPod Mini. They produced excellent sound and were comfortable to wear, once I got used to a cloth-wrapped cord that connects the two earpieces and is meant to be draped behind your neck.

The big downside of the Ety8 is this: They are ugly. They are relatively large, black rectangles that look like matchbooks pasted onto your ears. If you can get over that, the Ety8 wireless earphones for the iPod are great.

Email me at mossberg@wsj.com.