What headphones?

Etytomic are ok. Especially good at isolating your ears from ambient noise. I returned my ER4's after a week -long audition. For $140 the ER6's are the "bargain" of the line, especially compared to the ER4's ($270). But NEITHER provide much LF compared to most other “mediocre” over-the-ear designs.

Ditto plus the ETY's

I have a pair of the ER4s too, and they are great! I would recommend the ER4ps though if you are running them from your computer. Or if you don't want to spend the 269 bucks, they have a new "reasonably priced model." Check our headroom.headphone.com.

For under $100 I would go with the Sony MDR-V6. It is a closed type headphone that helps to block out noise and can be easily driven.

It's above your price, but the Etomatic ER-4s are fantastic. If you decide to go for more $$, I can highly recommend these. I've been using them for years for travelling by air. They reduce the outside noise by about 25 dB, and they sound great.

Have you considered the Sennheiser HDC 451-1 headphone with the noise-cancelling circuitry? The headphone is light, comfortable, and the noise-cancellation system works very well in environments that have a steady-state noise in the background. I use this headphone whenever I fly, and it virtually eliminates cabin noise. Audio Advisor sells this headphone system for $100. It might be just the ticket for you.