simple logic question

emma123

hi, i need help in understanding something on sound. if admam works near a jet plane that is taking off and experiences the sound level of 150dB. then the protectors to reduce the sould level to that of a chain saw, what decrease in dB is needed? i think it's 40 but i am not sure.
and also if Adam hears something that sounds like a whisper then what would a person w/o protectors hear? is there even a difference....