Chiara Del Core 26 feb 2021 Articles 0 comments

The acoustic project: between legislation and design

One of the fundamental aspects aimed at ensuring individual well-being inside buildings is represented by environmental acoustics. In construction, the correct acoustic design aims to contain the noises generated by external and internal sources with respect to the home environments. The multiple soundproofing solutions concern the structure of the building but also everything that contributes to characterize it from the point of view of furnishings and accessories. As regards the Italian territory, the UNI 11367 standard designates a subdivision of the buildings according to the acoustic class to which they belong. This classification is useful to ensure a more correct design in terms of acoustic comfort.

Below is an explanatory guide on the fundamental principles of acoustic design.

Noise pollution and measures to minimize it

Noise pollution is an element that must be assessed from the early stages of the design process because in addition to being a cause of disturbance, it represents a problem that affects the health of the individual. In fact, many studies have shown how annoying noises generate problems related to stress, sleep and hypertension. For this reason, it is necessary to act appropriately both on the sources of noise and on the acoustic insulation of the building.

Noise can be produced by numerous sources external or internal to the building. In addition, it should be noted that each building type is different in this respect both for its intrinsic characteristics and for the intended use that distinguishes it. In the first case, these are sounds coming from the context, more intense within the urban scenario: car horns, traffic, trams, construction sites, the presence of large road arteries. As for the noises present inside the housing unit, the most common are those coming from conversation, shocks, systems such as washing machines, dishwashers, boilers, ventilation systems and taps. The presence of elevators and freight elevators in the stairwells of buildings can also be a source of unpleasant noise.

Depending on the type of noise and the source that generates it, it will be good to study the most suitable solution to best mitigate the disturbance for the human ear. In this regard, it is necessary to distinguish between sound absorption and sound insulation, concepts that are often confused with each other. The first is aimed at counteracting the sound that is reflected within a single environment, through the insertion of fibrous materials that will make up the walls and false ceilings. In fact, these materials have the ability to assimilate sound and prevent its diffusion within the environment. In other words, it is a question of containing internal reverberation and for this reason the sound-absorbing solutions are particularly suitable for buildings intended to accommodate large flows of people: offices, recording studios, theaters, bars and restaurants. Among the most common fibers are the mineral ones, those with a natural base and the synthetic ones: they range from rock wool, cork, up to expanded polyurethane, respectively.

It is good to specify how often an optimal acoustic insulation intervention requires the simultaneous presence of sound-absorbing and sound-insulating solutions. The latter represent the most suitable measure to contain the transmission of sound between several neighboring environments and between exterior and interior. In this case, the material is considered a real barrier that blocks the entry of sound and reflects it in the environment in which the source that generates it is located. To intervene in this way, we usually proceed with solutions that combine wood fiber with rigid sound-absorbing panels.

UNI 11367: Italian legislation on acoustics

With regard to noise pollution, the Italian legislation begins to make its way around the 90s, when, thanks to the introduction of specific decrees, the design sensitivity in terms of noise containment in buildings increases. Some "limit thresholds" are thus defined within which it is necessary to place oneself to ensure the user's psycho-physical well-being.
Given that the decibel represents the unit of measurement for quantifying sound intensity, the limit value of 50 dB is defined, beyond which the sound is perceived as a disturbance for the human ear.

Summary table of the noise intensity expressed in dB

Precisely with regard to the limits that must be respected to avoid unpleasant noises, the DPCM of 5 December 1997 was introduced, which defines the passive acoustic requirements of buildings and is still currently in force. The decree establishes the values that must be respected in order to obtain an acceptable acoustic comfort with respect to the noises between housing units, external sounds and those generated by systems and activities of different types.
These limits vary depending on the intended use of the property and for this reason, the buildings are classified into categories:
  • residential buildings-category A
  • offices-category B
  • hotels and similar-category C
  • hospitals and nursing homes-category D
  • schools-category E
  • cult and recreational activities-category F
  • commercial activities-category G                                                                                                                                    

Furthermore, according to the peculiarities of the property and the performance of each of its components, the UNI 11367 standard defines its acoustic class. Overall, the individual components must comply with the defined performance standards, in acoustic terms. Acoustic design is mandatory in the case of new buildings or urban restructuring interventions. As regards the construction from scratch, at the end of the works it is always mandatory to verify compliance with the limit values or alternatively acoustic testing.

To learn more about the acoustic design of a concert hall click here

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