I can’t give you dB but I can say the following: 1) these are not designed as noise canceling earphones, they are just standard earphones with a mic. 2) Having said that, when wearing the earphones, if someone is talking to me out of my visual field, I am unaware they are talking. For loud sounds such as machinery, they greatly dull the sound. Of course this is all susceptible to the volume of the media you are listening to.
Just remember blasting the volume in earphones to drown environmental sounds can damage your hearing (friendly psa).