Sound absorption is measured in decibels where the higher the number, the greater a silencing effect the material has. I looked around for the sound absorption numbers on a few materials and found these:
There are some good more wall and material types along with their ratings on the Sound Transmission Class wikipedia page. For reference, at 50 db, “very loud sounds such as musical instruments or a stereo can be faintly heard; 99% of population not annoyed” and at 60 db, “superior soundproofing; most sounds inaudible”.
It seems that with both straw bale and CEB walls will provide significant sound proofing and that the weakest link is likely going to be in the windows and doors.
This is how people who are really picky about sound proofing do it: .