Ask HN: Do headphones exist with noise muffling capabilities?

People constantly post about how distracting open-plan offices are. The solution that is often proposed, noise cancelling headphones, don't really work because noise cancelling headphones stop background hums, not the sound of talking. Actual earmuffs DO block sporadic sounds like talking. However you can't really wear earmuffs in an open plan office (that would be weird, and also earmuffs don't play music).

What would be amazing, would be headphones with earmuff material between the earpiece and the outside of the headphones. Then you can listen to music without any sound bleeding in.

If anyone is looking for a hardware startup this may be a good idea. I would pay good money for this. I've tried the usual recommendations eg Sennheiser HD280's but the sound muffling isn't that high.