The isolation of a simple barrier is defined as ten times the logarithm of the inverse of the transmittance coefficient. If we plot this coefficient based on the frequency, we will see that a barrier does not isolate equally across the range of frequencies. Five different zones are distinguished from isolation of a simple barrier :
Zone controlled by the rigidity: The isolation diminishes with the frequency and is at very low frequency.
Zone controlled by the resonance: It begins with the frequency of the first resonance of the barrier and it finishes with approximately double this frequency. It presents minimum of isolation.
Zone controlled by the mass: In this zone the isolation is proportional to the superficial mass of the barrier and it increases with the frequency 6 decibels by eight. The isolation increases to 3 dB when doubling the superficial mass of the barrier.
Zone controlled by the factor of losses: It begins in the critical frequency of the barrier, where the isolation drops drastically. Later it increases with a relation of 9 decibels by eight.