One of the more progressive segments in headphones are the Noise Cancelling Headphones designed for use in noisy environments such as planes, trains and…well even noisy work places. Up until now, if you wanted a quality Noise Cancelling headphone, you had a choice of three Sennheiser models and a few other models from the likes of AKG and Bose. (Yes I am skipping over the many cheap and nasty products out there, they simply do not work well)

In recent years we had a new contender, the Audio-Technica ATH-ANC7 and now it's replacement, the ATH-ANC7b, along with some exciting new Sennheiser models: the Sennheiser PXC 350 and Sennheiser PXC 450 which are both full size headphones, unlike their previous models.

So how do they work?
Active Noise Cancelling is based on the principle of phase inversion, where sound waves are cancelled out by their own 180° phase inversion. In other words, the headphones 'listen' to the ambient noise around you via a built-in microphone, and then 'invert' the sound wave and apply it to the sound from your source, which 'cancels' the noise.

Sennheiser PXC 150 and PXC 250
The Sennheiser PXC 150 is the base model in the Sennheiser line up with the Sennheiser PXC 250 being of the exact same specifications in terms of Noise Cancelling circuitry and ear pieces. The difference between the two models is that the PXC 250 folds and so it is a little easier to carry around. The finish and ‘look’ of the PXC 250 is a little more up market as well but essentially they sound the same.

So, how good are they? Keeping in mind they are essentially a Sennheiser PX 200 with NoiseGard added, they are pretty good, bass is a little ‘polite’ in that is is not the most obvious part of the sound field you notice, but generally they are well detailed. There is a slight bass boost when you engage the Noisegard circuitry, no doubt to compensate for the noisy environment robbing you of bass!

Comfort is where these are great - easy to wear for hours on end on that long flight to Europe, your ears never get ’sweaty’ like full size headphones can sometimes do and of course they are much lighter in weight and you can even fall asleep with them on and not be disturbed.

But, there are better sounding noise cancelling headphones to be had. Also of note, is the rather large NoiseGard circuitry which is the size of two AA batteries end to end and can not be removed, so if you are using them without Noise Cancelling turned on, you are stuck with it!

Sennheiser PXC 300
OK so you love the idea of the small sized PXC 250 but you want better sound because you are a more discerning music lover right? Well the Sennheiser PXC 300 was made for you! It has the exact same size and folding mechanism as the PXC 250, but with improved drivers and a newer NoiseGard Advanced system for noise cancellation. Finish is also improved with the metallic trim on the ear pieces.

The sound improvements they have made are in the area of bass response, and they have done a great job. Bass reproduction is very good for a driver of this size and provides a very full sound stage, but it never sounds overly heavy in the bass so it is not bass for bass sake. Nice job Sennheiser, this is a great choice for those looking for an easy to carry, high quality headphone with sound that suits the true music lover.

Sennheiser PXC 350 and PXC 450
As good as the previous models are, some people insist on having a full size headphone when they travel, and to answer that request Sennheiser released two new models in 2007: the Sennheiser PXC 350 and the Sennheiser PXC 450.

They both use NoiseGard Advanced, so the Noise Cancelling ability is very good. They are both identical in design and are full size headphones so they have substantially large drivers, and therefore delivery exceptionally good sound with deep bass performance.

The level of Noise Cancelling on the PXC 350 is 85%, and 90% on the PXC 450 which also features a similar technology to the Shure SE530PTH in that it has a ‘TalkThrough’ feature. Essentially you do not need to remove your headphones to hear someone talking to you, simply push a button and a microphone is turned on to hear what they have to say.

Needless to say these headphones delivery the best sound here, and the PXC 450 is a true Audiophile grade headphone, offering truly sublime audio quality and absolute luxury and comfort. If you want the best, buy the PXC 450, simple.

Sennheiser PXC 310 & PXC 310 BT
The new Sennheiser PXC 310 series launched late in 2009, offer similar portability to the PXC150, 250 and 300 models being only slightly larger, but with even greater sound quality and performance. Both use Noisegard 2.0 Noise Cancelling technology to remove upto 90% of the envirnmental noise around you.

Sound quality too is improved over the other portable models, with a frequency response of 15-22kHz for full clear sound. The PXC 310 BT offers the same performance but with the freedom offered by Bluetooth connectivity.

Finally, they both offer the same TalkThrough feature of the top of the line PXC 450, allowing you to have a conversation with your neighbor without having to remove the headphones.

Sennheiser MM 450
The Sennheiser MM 450 is the headphone of choice for anyone looking for the ultimate all in one solution for use with a mobile phone and for air travel. Combining the same form factor as the PXC 310 BT, the MM 450 incorporates the same Noise Cancelling ability, and adds integrated controls for use with your mobile phone.

Once again, the TalkThrough feature is here, and the ability to connect by cable to either your iPod or in flight sound system, and of course via bluetooth to your mobile phone. So if you only want one headphone in your life, it has to be the MM 450.

Audio-Technica ATH-ANC7b
The first thing you notice about the Audio-Technica ATH-ANC7b is the stunning build quality. In terms of size they fit very neatly between the Sennheiser models - yes they are a full ear covering headphone, but they are far more compact that the Sennheiser PXC 350 and PXC 450 models.

These headphones offer noise cancellation on par with the top of the line Sennheiser models, as for sound quality they are very good, but not as good as the PXC 450, but then they cost far less too. So why would you buy them? Well if you want a headphone that provides excellent Noise Cancelling, covers your ears completely but find the PXC350 and PXC 450 more than you need, then these are the ticket!

Audio-Technica ATH-ANC3
The Audio-Techncia ANC3 is a product which falls into two categories as it is both a Noise Cancelling headphone and an ear-canal headphone. They offer a viable alternative to both products by being the smallest Noise Cancelling headphone we sell, and as such is the easiest model to take with you on overseas trips.

Sound quality is good, ease of use and comfort are also good if you are a fan of ear-canal headphones which 60% of Australians clearly are base don national sales. So,they are easy on the ears AND the wallet and fill a very unique niche in the market.

Audio-Technica ATH-ANC1
The release of the Audio-Technica ATH-ANC1 late in 2009 has really heated up the Noise Cancelling market. Do not let it's low price sway you, this is a very good headphone. The Noise Cancelling is very good, and the sound reproduced by this light weight and compact design is excellent.

This headphone is superior to the lower end Sennheiser models, and quite frankly makes them look very over priced. So if you are looking for a good performing Noise Cancelling headphone that offers great sound, then look no further!

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