I'm not very musically literate to stuff like that so I honestly don't know if I'd know the difference between good and bad haha. They were not expensive and obviously don't have the quality you'd get with Bose or Beats or something. But I never noticed any sound problems when I used them.
Im not totally sure how to objectively answer that question...I turned my iPhone's volume all the way up and you could hear the music quietly coming out when they were sitting next to me. I couldn't handle it any louder than having the volume half up when they were in my ears. So I guess they are decently loud?