SOUNDPROOFING REDUCTION BASICS
Sound is heard through the weakest link, adversely the loudest sounds are heard; Example if you are in a group of people who are talking you must talk louder in order to be heard. The ability for something to reduce the amount of sound that passes through it is measured in STC or Sound Transmission Class. It is expressed in 0-100. 100 is complete soundproofing, to achieve an STC 100 it would mean no windows and concrete walls about 3 feet thick.