[NiHaoMike]

The interesting part is that just two years after the thread was started, TRRS headsets started becoming very common thanks to the iPhone and other smartphones.

 

[Duncan]

Now my question is, are the 5 poles used for conducting power for "active noise cancellation" or for Hi-Resolution audio "Hi Res Audio"?

Having bought the EX750, and having also just ordered the NC750 I can say that the NC750 has an extra fifth ring to cater for the stereo mics (so, assuming left / right input, left / right output and ground) - the EX750 only has four poles due to having the electronics for noise cancelling on the cable, so only needing the standard android / IOS connectivity (there is no remote functionality on the NC750 else that would get even more complicated!)

For what its worth, if it floats your boat having the NC750 allows you to record sound in stereo on the Z5 - weirdly handy if you're at a gig I guess

 

[returntosennder]

I actually came across a pair of Sony noise cancelling earphones with a 5 pole TRRRS 3.5mm plug back in 2009 (they were bundled with a Sony Vaio laptop).
 
For active noise cancellation, there are small microphones placed inside the earpiece housing facing away from speaker. The signal from these microphones is then flipped 180 degrees by a digital circuit (which is the AA battery powered thingie) and fed back into the earphones/headphones. As a result the interference is completely destructive and the noise coming from outside is cancelled out.
 
Conventionally, the circuit that performs the flipping and adding is either housed inside the headphones (Bose QC line), or is in a separate battery powered box in the cable. In those cases, a standard 3 pole TRS 3.5mm plug can be used, permitting the use of the earphones/headphones with most standard audio devices.
 
In several Sony applications of the technology, the processing is performed at the source (inside the laptop/smartphone). So, two of the five poles of the TRRRS jack are for the microphones, while, the other two are for the standard audio signal. The flipping and adding is performed by the audio circuitry inside the device, either in the digital domain or in the analog domain (I'm not sure which). However, this means that the noise cancelling feature (and in many cases, the earphones themselves) can't be used with any other device.
 
I hope that this answers your questions.
 
Regards
Sennder