I see the initials db, IIC and FIIC referred to when reading about sound reduction, what do these mean?

• db is a measurement of sound levels. Example: A pneumatic drill gives off a sound around 130 db and conversational speech around 70 db.
• IIC (Impact Insulation Class) is a method for determining the transmission loss of impact sound through a floor. Usually, the results found in a sound laboratory test.
• FIIC (Field Impact Isolation Class ) is similar to IIC but usually, the results are found in actual on-site field tests.