[bpfiguer]

Replacing my Shure SE535 with the Sennheiser IE800 IEM has the disadvantage of getting much lower noise isolation but with better sound quality.
 
I tested reducing the noise by covering the IE800 with a passive earmuff with high Noise Reduction Rating (NRR: 31 dB) like the 3M PELTOR X5A (http://www.amazon.com/3M-Peltor-X-Series-Earmuffs-X5A/dp/B00CPCHBCQ/ref=sr_1_1?ie=UTF8&qid=1411526972&sr=8-1&keywords=PELTOR+X5A)
 
Findings:
- Air noise due to air flow and vented IEMs is gone
- I can barely ear noise even inside the subway
- Cable microphonic is gone (Earmuff presses each channel cable)  
- The IE800 remain inside my ears without moving out (less mechanical stress for the cable/IE800 junction: upper IE800 cable can not be replaced)
- The earmuffs are comfortable but unfortunately they look weird (pocking out from your ears). I look like wearing Beats headphones.
- NRR 31 dB is comparable with the obtained using Etymotic Research ER-4PT IEMs
 
How to talk or hear people talking to me when I use the IE800+earmuff?
I use a Shure PTH (Push to Hear) module which has a microphone activated by pressing a button and is connected to the IE800 and portable amp line-out.

 

[Trebbleclef]

Fantastic review bpfiguer.  Thanks!  I have a pair of the ie800s purchased and waiting their arrival here in San Diego.  Being aware of a potential microsonic problem I figured I would use my Belton Ultimate 10's on the Sennheisers like I have done with my ie-400s when I want to block out all intrusive noise.  One's ears tend to heat up with the noise protectors on so you have to take more frequent breaks. But using them in public places makes for an appearance no different from someone wearing a pair of NAD Viso HP-50s which I own. Remember the NAD slogan on the box is that we're not concerned with your lifestyle but concerned about your ears.