Although acoustics pertains to very broad fields, including infrasound and ultrasound as well as sounds, this article will only deal with sounds to which human hearing is sensitive within a building. With this in mind, any activity, building or infrastructure may produce noise or be attacked by noise. In terms of buildings, noise pollution like traffic noise, impact noise, conversation, equipment, etc., are nuisances that can degrade the quality of life of their occupants.
Studies have shown that 54% of French people feel uncomfortable with noise from the outside neighborhood if 85% are bothered by noise from their homes. For these reasons, noise control, based on the study of the sound environment or the use of the existing or to be built building, has become an essential issue. This results in regulations and standards specifying the minimum acoustic performance to be achieved in buildings, to ensure appropriate acoustic comfort for their occupants. Thus, acoustic performance is expressed by a large number of indicators characterizing products, buildings, phenomena, systems, etc., related to the acoustic insulation of a building. In addition, some concepts can make it possible to better understand the physical quantities and their values, which are used to describe products and systems as well as regulatory requirements.
Concepts and minor quantities related to sound
In a sound wave, the pressure fluctuates several times about atmospheric pressure. This number of fluctuations per second determines the frequency of the sound and is expressed in (Hz). Per second, the time between 2 flips. The longer the time, the lower the frequency, to generate a low sound. On the contrary, if it is short, the frequency is high, to generate a high-pitched sound.
The hearing threshold of the human ear perceives sounds of frequencies between 20 and 20,000 Hz. For example, we can mention hum at low frequencies (from 20 to 200 Hz) poorly perceived by the human ear, and kettle whispers (from 2,000 to 20,000 Hz). Speech and music, well perceived by the ear, are at medium frequencies (from 200 to 2000 Hz). The target frequencies as part of the acoustics in the building range from 100 to 5000 Hz.
Noise is analyzed with a noise spectrum at the general sound level. Still in the acoustics of the building, we rarely encounter a pure sound, of one frequency and strength of its own. Instead, we encounter associations of sounds of different frequencies and energy levels, and that is noise.
Acoustic measurement performed in a building or laboratory with a sound level meter provides a spectrum of noise. This represents the sound level for all frequencies that were measured. The noise spectrum is analyzed and then mathematically processed to be the general sound level in dB or dB (A), dB (A) being derived from the weighting considering the sensitivity of the human ear. This general level of sound makes it possible to classify, compare and add vocal performance between them.
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Acoustic comfort refers to a subjective idea depending on each individual's perception. This is influenced by various factors, because the same noise can be perceived by the individual as a noise nuisance due to the duration of exposure to that noise, its appearance during sleep or the memory related to that noise. Thus, it is necessary to take into account these concepts from physiology and psychology in terms of acoustics (the field of psychoacoustics), since they highlight the difficulty sometimes of dealing with problems of noise pollution. Moreover, the human ear, a human organ that is still active, is not purely rational.
Noise meter and rules for adding noise levels
Rules for adding noise levels
The classic noise level addition rules do not apply to noise level. For example, two identical and simultaneous conversations, having a sound level of 50 dB, will not give a sound level of 100 dB, but a sound level of 53 dB. The possible additions to noise levels at small or large deviation are expressed below.
• The case of noise levels with a level deviation greater than 10 dB
• If the difference in noise levels exceeds 10 dB, the highest noise hides the lowest. This is a "masking" effect where the sound is made inaudible by another. For example, 85 dB noise plus 80 dB horn noise gives 95 dB noise.
• Noise condition from adjacent levels, i.e. deviation minus 10 dB
If the noise levels are nearly identical, the resulting noise level is evaluated by adding a certain value to the highest noise level. The following table summarizes the most common cases.
Volume of noise levels
For common noise, the magnitude of noise levels, according to the perception of the human ear, ranging from the quiet atmosphere of a low-pitched conversation to the noise of an aircraft on takeoff, is as follows:
• As for light noise such as wind rustling in the leaves, flat is quiet, levels between 10 and 40 decibels.
• According to a calm atmosphere, the approximate level is 25 decibels.
• For low conversation voice, the level of 30 dB.
• In the case of a refrigerator, a quiet desk or a normal conversation, the level is 40 dB.
• If it is a washing machine, the level is 50 dB.
• With TV, very busy street, levels between 60 and 80 decibels,
• For sounds of a car, passing train or loud music, levels range from 80 to 100 decibels.
• No noise from boiler making workshop, hammer, levels between 100 and 130 decibels, etc.
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The case of simple walls: empirical mass law and critical frequency
We are aided by simple walls, to compose by one article. Their acoustic performance depends on the nature and surface mass of the latter. According to an empirical law called the "law of mass", the indicator of sound attenuation varies with frequency. and so
In addition, the critical frequency refers to the frequency at which the wall generates sound attenuation at the lowest value. Besides this frequency, the attenuation index increases linearly.
The critical frequency must be less than 100 Hz for the wall to perform acoustically. In practice, this frequency can be reduced by improving one's wall thickness.
Case of double walls: the effect of mass spring mass and resonant frequency
To improve the acoustic performance of walls and reduce their weight and thickness, double or light wall systems can be used. They have two walls, one separated by an air vacuum or insulation. They have much better acoustic performance than single walls of the same thickness.
The resonance frequency is a function of the thickness of the block and the nature of the elements (material and air/gas slice) that make up the wall.
In order for the double wall to have optimal acoustic performance, the resonant frequency must be less than 100 Hz. It is possible to move the resonant frequency of a double wall by increasing the space between the siding, the siding block or by changing the nature of the insulation. For example, doubling the siding mass provides an insulation gain of 3 to 4 dB.
Noise propagation media sources
Identifying noise sources, and understanding their propagation media are the first elements to be identified before designing or improving a building's acoustic insulation or room acoustic correction.
We can distinguish 3 main sources of noise (airborne, hard and equipment noise) in building acoustics.
• Airborne noise
This is the noise emitted by a source that does not have contact with the built structure. Airborne noises spread through the air before the walls of the room shook. Each vibrating wall in turn vibrates the air inside the building. This is how the sound passes through the wall. Airborne noise can be indoor airborne noises, formerly called pink noise (generated by conversations, television...). It can also be external noise, formerly called road noise (noise caused by road, rail or air traffic...).
• Hard noise or impact noise
They arise from direct vibration of the structure. Thus, the shocked wall enters the vibration and vibrates air from neighboring buildings. They are also referred to as shock sounds or bumping sounds in cases of footsteps, falling objects, etc.
This type of noise is transmitted by ambient air and vibration of walls and equipment. Equipment sounds come from elevators, ventilation ducts, various hydraulic networks, etc.
Noise is mainly propagated according to one or more of three modes of propagation namely scattering, reflection and transmission.
In free space, scattering of sound energy can be observed, which leads to a decrease in the noise level with distance. The spatial decrease in airborne noise can be measured according to the noise source.
In the free field, in an open space, the sound level drops by up to 6 dB each time the distance from the source is doubled.
Thus, for the case of a point sound source (factory, disco...), where the buildings are closed, this value is obtained only if the buildings are free of reflections.
On the other hand, for a linear source (road and rail infrastructure) where there is no mask, the noise level can drop by up to 3 dB every time the distance from the source is doubled.
• Propagation by meditation and sucking on an obstacle
In the event of an obstacle, there is a phenomenon that resonates from a portion of the vibration on the walls and obstacles encountered.
• Diffusion by transmitting vibration to the material
Noise is propagated by solid materials, such as walls and structures, as described above.
Acoustic therapy for buildings
Room acoustic treatment should take into account all possible sources of noise propagation from load to execution. In fact, acoustics make up everything. The acoustic treatment of the building, for acoustic comfort and compliance with regulatory requirements, should be based on an architectural design that highlights high-quality acoustic insulation, along with an acoustic correction adapted to the use of the building.
If in a room, an item has low acoustic performance, it will affect the performance of the entire room. This element may come from a design or implementation problem. It can be a wall that has a lower performance than the whole, a pit that generates airborne noise transmission, a structural component that can transmit equipment noise, etc.
Unwanted transmissions in a room are called "parasitic transmissions" if the elements that enhance their transmission are called "sound bridges".
Examples of stray transmissions are wall (lining) junctions, ceiling wall junctions, counter-drills, and structural elements touching equipment or non-mock nets.
When the room is isolated from noise from the outside, it is necessary to treat the inside of the room to reduce the echo of the sounds produced in the room. Voice therapy should always be considered without neglecting parasitic transmissions.
Isolation and correction
The purpose of sound insulation or sound insulation is to prevent the spread of noise from one room to another. It is a matter of treating the walls against external noise on the one hand, and on the other hand so that the noise emitted in the room in question does not spread to the outside. Sound insulation is based on modifying the sound presentation of a room to adapt it to its use (home theater, bedroom, etc.).
In the construction of acoustics, it is necessary to consider:
• sound insulation, the purpose of which is to protect against noise emitted from outside the room in question,
• Acoustic correction improves acoustic comfort in the room.
In practice, the building suffers from significant noise pollution, of internal or external origin. Thus, to be effective, sound insulation must take into account architectural design, air-conditioned products and systems, and careful execution.
Basic principles of good sound insulation
In order to achieve tuberculosis isolation,
Yum, we can mention three basic principles, namely the law of mass, the universal quartile mass law, and the law of sealing.
• Law of Mass
The principle is simple, the heavier it is, the better it is to isolate it. Concrete, with equal thicknesses, insulates a concrete section better than a tiled section since grout is at the same size, concrete is heavier than grout. The heavier the material, the more force it has to attenuate the transmission of sound waves. Thus, by doubling the wall thickness, one can obtain sound attenuation from 5 to 6 dB. However, not all constructions allow this process, as it requires significant overloading as well as the need to reinforce the foundations, to name a few.
• Law of mass spring mass
By combining certain materials, the principle of "mass spring mass" can be applied. This principle consists in the use of double walls such as plaster, separated by air or flexible insulation, which absorb and dissipate energy. When the noise hits the first block, it starts to vibrate. The spring between the two layers has the role of intercepting vibrations and acting as a shock absorber. The noise is then greatly attenuated as it travels to the second block. In internal regeneration, this solution guarantees an effective treatment without overburdening the structures in any way. Systems that use this principle are lighter and more efficient because they provide a gain of 6 to 8 decibels.
• Law of Seal
This law states that when air passes through, noise passes through. Windows, door bottoms and poor sealing at the foot of the partitions are all causes of waterproofing failure, which should not be neglected if you want the insulation to be satisfactory.
Appropriate solutions for sound insulation
in the building
Sound insulation protects against various types of transmission mentioned above and provides conditioned responses to windows and glass (to counter external airborne noise, from the street or garden), to doors (to counteract indoor airborne noise, from room to room), to walls and partitions (to counteract the same types of noise as It is with doors), for intermediate floors (to counteract the noise of bumps or shocks, from one floor to another).
When it comes to windows, insulation against external noise is based on joints and glass.
Indeed, in the field of building acoustics, it is important that the window be closed and well formed. The quality of the seals must be checked so that, when they prove to be defective, they must be replaced.
Later, it is necessary to emphasize the thickness of the glass and to choose in particular for double glazing. The recommended high performance double glazing is Type 10-6-4. This means that it consists of a first sheet of glass 10 mm thick, an air slice of 6 mm and a second sheet of glass 4 mm thick.
In the case of renovation, a double window would be an interesting alternative to changing the current window, in other words, placing a second window a few centimeters away from the current window. However, even if this solution provides better sound insulation, this device can be a source of condensation, which can appear between the two parts.
For better results, we can choose acoustic laminated glass, most commonly in PVB or polyvinyl butral. This material is similar to that used for windshields or burglar-proof windows, but it also has additional features, useful for sound insulation.
In some cases, the use of double glazing is not mandatory. And single thickened glass or acoustic laminated glass explained above, will ensure good sound insulation.
As for the doors, the main disadvantages of sound insulation are poor sealing and low mass.
So, for an existing door, the first thing to check is the end seals. The closure must be tight, even at the threshold. Elastic or metal terminal seals can be found, as well as acoustic threshold bars.
When the door is completely closed, it is possible to add a block to the sheet. As a simple principle, the heavier the paper, the more inert and insensitive to sound vibrations. One can find many dense products that are glued to a sheet of weighted paper such as medium plates or plaster. However, it is necessary to pay attention to the mechanical strength of the door and the additional weight that can be supported. It is also possible to find acoustic door blocks on the market. These are doors with armed acoustic insulation. In addition to a wide range of models, you can also choose between different levels of sound attenuation (ie the number of wet decibels).
To ensure the acoustic insulation of the walls, one can choose from among a few installations that are based on the principle of "mass of a mass spring" by being sure to choose the insulation that will serve as the spring and the elements that will play the role of the block.
These are the installation of ready-to-use panels, the installation of panels on the frame (wood or metal) and as an extreme solution to the installation of a counter-section.
For ready-to-use panels, studs can be applied with wall glue on one side, and plaster on the other, as a coating. In the center will be placed soundproofing. Improve system performance by adding a second plaster glued to the first or increasing the thickness of the insulation.
As for the panels on the frame, it is preferable that the latter be fixed between the floor and the ceiling, without affecting the wall. The space between the column and the frame is to be filled with sound insulation if plaster covers everything. The performance of the system increases by using the second plaster glued to the first or by improving the thickness of the insulation.
By installing the counter section, the insulation will be inserted between the original section and the new brick or grout tile section.
Types of insulation to use for spring
For sound insulation, the insulation chosen is mainly mineral wool and natural wool. Mineral wool has already proven itself if rock wool is still more effective than glass wool. The performance of natural wool is related to the use of dense boards such as wood wool boards at 55 kg / m3, cellulose
At 70 kg / m3, wood or cork fibers. On the polyurethane side, acoustic polystyrene has quite consistent performance.
Note that insulators play the role of a "spring" in the "mass spring mass" sound insulation principle.
As for the "masses", the first is the existing wall if the second is the lining that underpins the flexible insulation. Generally, this second block comes in one or more stucco, counter-section, one or more dense composite shingles, or a mixture of stucco and wood. There are also gypsum and cellulose sheets that have inert properties while being denser than usual plaster, and are more performing from an acoustic point of view. One can also find composite panels formed from gypsum board and insulation based on cellulose or flax straw.
The simplest action against my footsteps is to root the problem at the source. In other words, you can choose soft floors such as carpets or rugs, which should absorb the shock before transferring it to the floor. However, this solution will not have any benefit to airborne noise.
Floating floor covering with foundation separated can also be an effective solution against footsteps. For example, we can mention the floating parquet floor laid on wood fiber boards. The foundation can have a thickness of a few millimeters to a few centimeters. This last option (a few centimeters thick) can bring a clear improvement in terms of airborne noise if it is concrete or dry, floating, laid on a layer of insulation, very effective against any kind of noise.
Intervention at the ceiling level
If we can't intervene at the floor level, we can try to solve the problem from below, at the ceiling level. The most common option would be a false ceiling with plaster and sound insulation behind it.
Plaster should be laid in such a way that it is as separate as possible from the ceiling. Metal rail systems with anti-vibration stabilizer can also be used. It is also possible to use wooden or metal rail cups with ordinary fasteners, provided that a separating felt is inserted between the frame and the plaster.
To determine the optimal method of optimal insulation for the building, it is best to call a professional, who will conduct an acoustic diagnosis.
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Principles and basic steps to be followed
Acoustic diagnosis is carried out by an audiologist. For this, it is based on a few criteria including,
• Determine the nature of the noise (is it indoor or outdoor air, impact, equipment?).
• Detecting the source of the noise, ie the channels or walls through which the noise is transmitted in order to be able to treat it.
• Assessment of perceived noise intensity (in dB) by in situ measurement. For this, it is necessary to determine the maximum acceptable noise level for a room or dwelling, and thus determine the isolation gain to bring,
• Determine the nature of existing walls to be treated, cinder blocks, hollow bricks, concrete, plasterboard tiles, honeycomb partitions, wooden floors, etc.
• Choice of appropriate solution and performance depending on the nature of the wall.
Meeting all these limitations is to ensure that any noise problem involved is remedied, with optimal chances of success, by selecting the best solution.
The importance of a phonetic diagnosis performed by a phonetician
In general, the simplest solution is the direct use of the insulation product or the installation company. However, a professional phonetician is able to provide a complete and qualitative study. It is first necessary to determine the sources of noise, their path and the weakest walls. Therefore, the expert can be bound to guarantee the result. Later, he or she can advise a transplant company to prepare recommendations and diagnostic recommendations. Therefore, the acoustic is no more and no less a specialist in the sound insulation of a building. Its main objective will be to put an end to various types of noise pollution.
To find the phonetics of your choice, you can search online directories on the Internet. You can also choose platforms to connect professionals and individuals. In any case, nothing beats the use of a professional recommended by his immediate entourage. Indeed, this process carries an undeniable guarantee of the quality of work and know-how of the concerned professional.
Subsidies for acoustic insulation works
in a building
The National Housing Agency finances acoustic insulation works that are part of work that promotes sustainable development (eg energy saving, water saving, sound insulation). These steps include, among others, working on the following:
• Improving the acoustic insulation of opaque floors, ceilings and walls.
• Reinforcement of insulation from glass walls such as double glazing or double windows.
• Improved sound insulation of noisy equipment.
• Implementation of air conditioning or refrigeration solutions aimed at improving acoustic comfort. This applies to buildings that are highly exposed to heat and noise.
Interference with undertakings shall include the supply and use of materials and equipment. Thus, direct purchase of materials by the owner cannot qualify for a subsidy from. To the labor costs, we can possibly add the main contractors' fees. In addition, there are also costs related to technical studies and any prior diagnosis.
The amount of the subsidy is calculated according to a rate expressed as a percentage. For the landlord, the support rate can be from 20 to 70%. This parameter varies according to the rental restrictions involved. For incumbent owners etc., this assistance corresponds to resources. In this case, the rate can be 20 or 35%, depending on the level of these.
Sound insulation and sound insulation: are they the same thing?
Even if it is intended to treat sound, there is a difference between sound insulation and sound insulation.
Sound insulation and its principles
Sound insulation ensures a pleasant sound to the dwelling. The methods, as well as solutions implemented for this purpose, aim to avoid excessive diffusion of internal acoustic energy. As such, we will try to avoid echoes of sounds by reducing the time they propagate against walls along their path. In other words, sound insulation is actually sound correction
Rather than a way to suppress unwanted noise. After as a principle of reducing the effect of resonance, set the sound absorption index of a particular substance or solution.
Sound insulation: the last resort of noise pollution
Parasitic noise mainly comes from our close environment, street, traffic ... For a period no longer subject to them, barrier based on the principle of mass spring block, and continuous is necessary. It is important that this barrier should not have any sound bridges or interruptions. Sound insulation is measured, which thus consists in suppressing, or at least reducing the intensity of noise, or decibels.
In general, proper comfort results in a fallout level from outside sound that does not exceed 35 decibels. The sound insulation of a dwelling must be considered from its construction, or even, from its architectural design, and implemented in a universal way. That is, it is not enough to insulate a few walls. It is necessary to insulate the entire dwelling, starting from the floors to the attic, through the walls.
Due to the inertia or sufficient thickness that it provides, the stone can provide sound insulation of the wall. It is also important to know that openings, doors and windows are strategic points for spreading noise. In addition to framing the sound tight, double or triple glazing helps reduce this excessive sound spread.