What is the meaning of psi,sccm,db? Application skills

Content:
PSI is a pressure unit, defined as pound/square inch, 145psi=1mpa
Mass flow unit SCCM, standard-state cubic centimeter per minute, standard ml every cent
Decibel is the sound pressure level unit, recorded as DB, used to indicate the size of the sound.
The faintest sound the human ear can hear is about 1 decibels, steady breathing sound and the leaves swing sound is about 10 db, waterfall Waterfall's stream sound is about 20 decibels, the soft-spoken conversation sound is about 20-30 decibels, the soft light music is about 40 decibels, the medium speech sound is approximately 45 decibels, Radio and television playback of the intermediate volume is about 50-60 db, loud noise and office noise is about 60 db, the city street noise is about 70 db, the children's call noise is about 80 db, bustling street noise is about 90 db, The noise of the truck is about 90~100 db, the roar of the motorcycle is about 105 db, the Thunder is about 110 db, the loudspeaker expands the voice is about 120 db, the sound of the jet engine emits about 150 db, the loud noise of the cosmic Voyage rocket in close range is about 140~170 db.

British units of pressure