Let's see- we want to block out noise but use earbuds to put noise into ears?
Yes, this is EXACTLY what we want to do! First, we want to block the physiologically damaging noise coming from the machines at ~90 db. Second, for those of us who enjoy music in the background at lower db, are not afraid of potential psychological damage of some lyrics, and don't need (or want) to concentrate on each musical note or word in the lyrics, we want to hear something other than the whine (now reduced) of the machines.
Regarding safety - if you don't turn off your machines when the cuts are done, regardless of whether you wear ear protection or not, change your habits or avoid distractions. Also, don't listen to music if it consumes you, because the machine might consume you instead...
I've been using IsoTunes for several years. Their earbuds fit my ears (while many regular earbuds don't - the inside of my ears have weird shapes...) because they are like foam, they do a very good job of blocking much of the noise and they let me hear the phone ring (and then TURN OFF THE MACHINE before starting a conversation).
BTW, I only listen to classical music. Pandora is my favorite streaming source.