Great Noise Cancellation Headphone

What is Noise Cancellation
Noise cancellation usually implies active noise reduction (ANR), although sometimes the passive ways to reduce noise can also be called by this name. Passive noise reduction uses sound absorbing material to reduce noise from going into your ears. They are usually bulky. In contrast, active noise reduction, or noise cancellation, works in a more "active" way. The headphone uses microphones to analyze the noise coming from the environment, and then produces the same noise in the headphone. This additional noise that the headphone produces is called "anti-noise", because it is exactly the opposite of the incoming noise (or, in technical terms, 180 degrees out of phase), and therefore can cancel out the incoming noise.

Noise cancellation headphones can achieve better noise reduction with much less bulky design. They can also be designed to reduce noise at certain frequency without affecting others. For example, headphones for airplane pilot block engine noise without interfering with conversation. However, noise cancellation headphones do consume electricity and therefore require a power source (usually battery). Also, it is known that high frequency noise cannot be cancelled as effectively as the low frequency noise.

The gold standard of noise cancellation headphones is the Bose Quiet Comfort (now in 2nd generation). However, the Sennheiser PXC line is widely regarded as the second best, with a much lower price.

What’s in the Box
The Sennheiser PXC 250 comes with a foldable headphone with very comfortable leather-like ear pads. The pads are quite small, about 1 inch in diameter. This size is large enough to cover the entire ear canal, but not too big as to press the outer ear (the auricle, in technical terms) and cause pain for glasses-wearers. The size and finish of the PXC 250 headphone is great.

The headphone connects to a tube. This is the noise cancellation unit, which includes circuitry, batteries (two AAA, not included), a switch and an indicator light. The switch is used to turn noise cancellation on and off. It should be noted that the headphone is fully functional even if the batteries are dead or missing. However, there is no way that you can bypass the tube (I would prefer that option), so you will have to get use to this piece. It does have a good belt clip. Remember the clip can rotate 360 degrees so make sure you find a comfortable position. For tall person who wears the tube on his/her belt, it is better to point the connections up. I would also like to point out that the noise cancellation function works even if you don’t connect the headphone to a sound source.

The PXC 250 also comes with a very nice carrying bag. The bag has two compartments. The main one is quite large for the headphone. I imagine that if you have an iPOD, you can throw it in there as well.

There is a nice surprise for you in the front pocket of the carrying bag. There are two adapters in this pocket. One for 1/4" connectors (like in home stereo systems), the other one, take this, for the airline style double connector. With the airline adapter, you can enjoy the in-flight movie with much better sound, not to mention that you don’t have to pay for the poor airline headphone!!

Noise Cancellation Works!!
I work in a noisy lab. Instead of making the lab less noisy by installing sound absorbing materials, the company decided that it is cheaper to provide this headphone to whoever complains about the noise. Needless to say, I complained!!

So I got the headphone, put in two AAA batteries (make sure the positive points to the switch), and turn the noise cancellation on. Even before I turn on the noise cancellation, the noise level was reduced noticeably, especially the high pitch noise. However, real magic happens when I switch on the tube. Immediately the noise level was much reduced. In stead, I start to hear a very low hissing. I also feel a little pressure in the ears, which tickles at the beginning, but became unnoticeable after a while. By reading a little bit on the web, I learned that this "sensation" is very normal for every noise cancellation headphones. Plus, when I connect the headphone and start to play some music, I can no longer hear the hissing, nor can I feel the tickle. So it is quite nice.

I even used it in at home. I have a noisy computer (a full tower with a few extra fans installed). The noise cancellation function on the PXC 250 works very nicely.

It should be pointed out that if you are in a very quite place, turning on the noise cancellation will actually introduce a high-pitch hissing that can get annoying, if you are not listening to anything, that is. My argument is that, in this case, there is no need for the headphone. If there is no noise to cancel, and no music to listen to, why do you still keep the headphone on? Sound pretty simple logic but there are people still do that kind of silly thing, and then complain that the headphone is no good—you can actually find one review like this on this site.

Listening Experience
I have used this headphone to listen to Rock, Jazz, Pop and Classical music. The sound is very pleasant, when the noise cancellation is switched on. For some reason, turning on that function also boost volume. The boost on the bass is more pronounced. The whole sound is just much fuller. With the switch off, the headphone’s performance is not that great.

So the lesson is to keep your battery fresh and always use it with the noise cancellation switched on. Just remember to turn it off when you are not using it.

Black iPOD-nano's Best Friend?
Did you know that the new black iPOD-nano does not have a matching black ear-phone from Apple? In fact, the black mp3 player comes with a WHITE Applie Official earphone!! If you think that is ugly, like I do, you would find yourself a black headset.

The PXC 250 fits in this role perfectly. The round plug fits the iPOD with the right style. Sound quality was great. Plus, you can put your Nano in the headphone bag to avoid damage.

Battery Life
There is no spec on this anywhere. The Bose uses one AAA battery and can last 65 hours. Since the Seenheiser PXC 250 uses two AAAs, I would expect it to last longer. My recent test shows that a pair of regular Energyzer alkaline battery lasted 135 hours, although the low-battery light started flashing at 100 hour. I am testing rechargeable batteries now.

Battery Test Live 2005.11.11.8:00am
A pair of new Panasonic Ni-MH rechargeable Batteries (rated at 780 mAh) is being tested now. The battery died around 65 hours. Unlike the alkaline battery, the blinking red-light only goes on for a few hours.