Sound insulation and sound absorption are the main features of the acoustic materials. Even though these two concepts are often confused with each other, they are actually completely different and it is very important to understand the difference between sound absorption products and sound insulation products.
ABSORPTION (OR SOUND ABSORPTION) MATERIALS
The main feature of the sound absorption products is not to properly reflect the noise, but rather to ensure it is reflected as less as possible and is converted into a different type of energy, e.g. heat. These products are useful to improve the sound quality transmission and to create the best possible environmental experience. For this reason, they are particularly suitable to be used in testing and recording rooms, where the sound of music must be perfectly clear and not contaminated by external noises. This is known as acoustic environmental treatment.
The most common sound absorption materials are generally the porous ones. The parameters describing their efficacy are: density, porosity, geometry, rigidity of the structure, mounting distance from the rear reflecting surface. All porous-type sound absorption materials ensure the penetration of the air (and consequently of the acoustic energy) into the material itself. The more rapid the air movement inside the material is, the more effective this type of sound absorbers is. For this reason, the absorbers reach the best efficiency when the sound-absorption material thickness corresponds to ¼ of the incident sound’s wavelength. A porous material is suitable for the absorption of middle and high frequencies since they have a much smaller wavelength; also a sound absorption product with a reduced thickness can be very efficient.
These products are often used for noise absorption or acoustic containment in gyms and wellness centers, meeting rooms, shooting ranges, studio recording rooms, offices and many other interior spaces. In the industry sector, they are particularly suitable for soundproofing and noise absorption in rooms, engine compartments, lock-ups, canopies, waste containers.
The sound absorption materials, when combined with acoustic attenuation products, provide the acoustic insulation for machinery, as well as for very noisy working environment.
ATTENUATION (OR SOUND ATTENUATION) MATERIALS
Sound attenuation products allow the reflection of the acoustic energy. The acoustic insulation reduces the transmission of a noise from one place to another, from the inside to the outside and vice versa. Referring to a house, for instance, the insulation prevents the external noises to penetrate the house, or it also prevents the noise produced inside the house to be transmitted externally, avoiding to disturb the neighbors. The insulation of a room or of any other internal space, is obtained through panels combining sound-absorption and sound-attenuation materials.
The structure of a sound attenuation panel is made of high specific gravity materials (lead, rubber, polymer membranes) and it represents the so called mass; combining the mass with sound absorption materials (the so called spring) the sound attenuation properties will improve even further. The so obtained panels are suitable to acoustically insulate the structural components of a building or, referring to the industry sector, to insulate both machinery and very noisy working environments.
SOUND DEADENERS
This type of products (chemical compounds) is specifically used for sound deadening of metal parts that, vibrating together, produce annoying noises.
Main areas of applications: in the automotive sector, it is used for covering some car body parts, such as bonnet, wings, doors, etc… that are particularly exposed to noisy vibrations, as well as in the nautical sector.
These products are largely used in the industrial sector too, to acoustically insulate machinery, elevator doors and cabins, and all those products in general that need acoustic insulation.
THERMAL INSULATION
By “Thermal Insulation” it is meant all the systems and operations needed to reduce the thermal exchange between two environments having different temperatures.
High level sound absorption materials are generally good thermal insulating products.