Thanks for your replies everyone.
I never invested in a bed vibrator to alert me when my babies cried, wouldn't it wake up my husband also?
My youngest is now 3 so I really don't need to wear my ha on at night anymore, I used to love sleeping in complete silence, but now since my girls are older my fears have turned from not being to hear them cry, to being worried about intruders in their rooms and such. We have regular baby monitors set up in their rooms and the receivers sit next to my bed.
I only wear one ha on at night and I take turns so that my ears get a rest. I don't think I would be able to sleep comfortably any more not being able to hear my girls.
My husband has perfect hearing but I swear he can sleep through anything! LOL