Acoustic insulation involves preventing sound from either penetrating or escaping through a surface. For this purpose both absorbent and insulating materials are used.

There are a number of basic factors involved in good acoustic insulation:

• Mass factor
• Multilayer Factor
• Dissipation Factor

In regard to noise transmission, there are two groups:

ACOUSTIC INSULATION AGAINST AERIAL NOISE

This is where the objective is for sound waves to lose the greatest possible energy levels on passing through the enclosure, thereby resulting in maximum insulation.

The acoustic insulation of aerial noise of a construction can be expressed in three ways:

• In a graphic form;  representing the insulation (R in dB) in relation to the frequency (F in Hz).
• In a table form; giving values to the frequencies and insulation
• Through a single value (Rw in dB).

The parameters which define the insulation to aerial noise in dBA are:

• RA: overall index of acoustic reduction of an element (value measures in a laboratory). The higher the RA, the better the insulation.
• DnTA: difference in acoustic pressure between interior areas (value measures in situ). The better the DnTA value, the better the insulation.
• D2m,n,T,Atr: difference in acoustic pressure in facades and roofs of traffic and aircraft noise. The higher the D2m,n,T,Atr value, the better the insulation.

ACOUSTIC INSULATION AGAINST IMPACT NOISE

The objective is to cut out the transmission of vibrations through the positioning of elastic and absorbent materials.

The following aspects need to be assessed:

• The characteristics of the source of noise. In other words the type of object hitting the floor.
• The floor structure.
• The type of final coating or finish final of the flooring. For example carpeting or soft flooring clearly assists insulation.

The parameters which define insulation against impact noise are as follows:

L nw: Overall level of pressure of the impact noise measured in the laboratory in dB. The lower the Lnw value, the better the insulation.

• L´nT,w: Overall level of pressure of the impact noise measured in situ in dB. The lower the overall level of L´nT,w, the better the insulation.