[cactus_farmer]

In my experience, while in-ear monitors's block out the high-end of external noise very well, they fail to block out low frequency noises like the rumbling of a bus/plane/train very well, leading to noticeably weaker bass...
 
I haven't tried active noise cancelling - is it any better?

 

[obobskivich]

Look at the isolation graphs from InnerFidelity - you'll notice two things:

- LF attenuation is not common.
- ANC headphones fare about as well as high-isolation IEMs.

It's just the reality of LF waves - they go everywhere, have a lot of energy behind them, and are hard to control without comparatively a lot of mass. Something like the Bose QC15 will do an alright job at killing some engine whine/rumble, but you will still get some of the noise. Also remember that it won't cancel out bone conduction or vibration, which will re-enforce the sounds you're hearing. There are some IEMs that provide a decent amount of isolation down there too, but you aren't going to get perfectly silent.

 

[kwkarth]

The FACTS of the matter are that Active Noise Control is THE only effective way to counteract bone conduction. ANC really does work, or I should say can work if done right. Passive means of controlling LF and bone conduction are not effective. If you have question as to why this is so, please feel free to ask, else I will assume you understand. ANC does not rely on isolation at all.