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Aa
Absorber
Absorbers are materials or structures that absorb sound. Porous foams and fibrous materials are often used to absorb airborne sound. Viscoelastic heavy foils are applied to solid structures such as thin-walled sheets to absorb structure-borne sound.Absorber class
Acoustic elements are assigned to one of the absorber classes A, B, C, D, or E according to a procedure specified in DIN EN 11654, whereby this assignment is based on the respective sound absorption coefficient. The choice of class depends on the acoustic requirements of a room, as the materials of the various absorber classes supplement the sound absorption already present in rooms in a frequency-dependent manner. The type of material and the extent to which acoustic elements are required therefore depends on the type of use of a room. Since balanced room acoustics also require the reflection of sound waves, sound-reflecting acoustic panels are also manufactured, which are classified as unclassified. The absorber classes are divided into highly absorbent (class A, rated sound absorption coefficient αw: 0.90 to 1.00), highly absorbent (class B, αw: 0.80 to 0.85), highly absorbent (class C, αw: 0.60 to 0.75), absorbent (class D, αw: 0.30 to 0.55) and low absorption (class E, αw: 0.15 to 0.25), while acoustic panels with a rated sound absorption coefficient of αw: 0.00 to 0.10 are considered unclassified.Absorption
Absorption comes from Latin and means to suck in or swallow. Absorption is the absorption of sound waves by an absorbing material.Acoustics
The study of sound and mechanical vibrations is called acoustics.Aging
Aging is the gradual destruction of elastomers by oxygen, ozone, light, heat, moisture, and high-energy rays, which individually or collectively can cause progressive irreversible damage.Airborne sound
Airborne sound is sound that propagates through the air by means of sound waves.
Bb
Building acoustics
Building acoustics deals with the effects of structural conditions on sound propagation between rooms within a building and between the interior of a room and the outside world. The following sub-areas of building acoustics are covered: structure-borne sound, airborne sound insulation, and sound insulation for technical and sanitary installations.Bulk density
The density describes the weight of the foam in kg/m³ (kilograms per cubic meter). The weight or density of the foam is also an indicator of quality: the higher the density, the more durable the quality. However, the density has nothing to do with the perceived degree of hardness. As a rule, lighter foams are cheaper due to the lower amount of material used.
Cc
Causing vibrations
Moving parts on machines, devices, equipment, and vehicles generate vibrations and noise. These are caused by uneven or rotating movements of unbalanced masses. Vibrations and shocks have a disruptive effect on the environment in the form of vibrations and noise.Cell structure of foam
Depending on the type of material or material treatment, the cell structure is open, semi-open, or closed. Closed-cell foams include cellular rubber and cross-linked PE foams, for example. Open-cell foams are usually PUR foams. In subsequent material treatment, such as reticulation, the cell walls are removed by means of a controlled gas explosion, resulting in open or semi-open cells, for example in filter foams.Cold foam
The best and most valuable type of foam is cold foam. It can be compared to natural latex foam and is usually produced using the block foam process. Cold foam is a polyether foam which, unlike standard foam, is classified as a highly elastic HR foam (HR = High Resilient). Cold foam has the following advantages: open-cell, high air permeability, breathable, irregular, coarse pore structure and high elasticity with a supple feel.Compression hardness
Compression hardness, also known as compression resistance, refers to the pressure required to compress a foam material. With a compression hardness of 60, 6.6 kPa (kilopascals) are required to compress the foam material to 40%. The compression hardness of a foam material describes its strength.Compression loading of rubber
Under pressure, the linearity limit is 15% deformation, based on the rubber layer thickness. The influence of the shape factor must be taken into account in every design of a rubber spring for the pressure range. The shape factor is defined as the ratio of the active pressure area to the free pressure area of the rubber spring. This is due to the prevented transverse elongation and thus the variable modulus of elasticity c of the incompressible material rubber.Compression set
The compression set (CS) is a measure of how elastomers behave under prolonged, constant compression and subsequent relaxation. A CS of 0% would mean that the rubber fully regains its original thickness, while a CS of 100% indicates that the rubber was completely deformed during the test and shows no recovery.Compression transfer molding (CTM)
In the compression transfer molding (CTM) injection molding process, the inserted rubber compound is injected into the mold cavities through channels when the press is closed. CTM tools consist of three parts (upper, middle, and lower). Since friction heat is generated during the compression transfer molding (CTM) process when the mixture is injected into the cavities, the vulcanization time is reduced. The transfer molding process is particularly well suited for the production of small rubber molded parts in molds with many cavities.CR Chloroprene rubber
CR chloroprene rubber is also widely known under the trade name Neoprene. CR rubber has fairly good ozone and aging resistance, but only satisfactory oil resistance. Thanks to its high chlorine content, CR rubber has good flame-retardant properties. CR chloroprene rubber can be used wherever good flame resistance, good chemical resistance, and good aging properties are required.Cross-linked foam
In cross-linked foam, the molecular chains branch out and are chemically and physically bonded together through polymerization. Cross-linking increases mechanical and thermal resilience. The cross-linked foams in our range include Plastazote PE foam, for example.
Dd
Decibel (dB)
Decibel (dB) is the unit of measurement for loudness.Difference between cellular rubber and foam rubber
Cellular rubber and foam rubber are often confused, but the difference lies in the material properties resulting from the different manufacturing processes. Foam rubber has open cells and a dense outer skin. Due to its outer skin, foam rubber is particularly suitable for use in applications involving increased mechanical stress and abrasion. However, if the outer skin of the foam rubber is damaged, it can become saturated with water. Cellular rubber has no outer skin, but instead has closed cells. This means that cellular rubber is always watertight and airtight. Foam rubber and cellular rubber are foamed rubber grades (EPDM, SBR, CR, NBR) and can adapt very well to the substrate, which is why they are mainly used for seals.Difference between structure-borne and airborne sound
Put simply, the propagation medium is the difference between structure-borne sound and airborne sound. Airborne sound propagates through the air in the form of sound waves. Structure-borne sound, on the other hand, propagates through solid bodies such as steel, concrete, wood, stone, etc. This includes, for example, impact sound or the noise generated by building services equipment.Diffuse and direct sound
Diffuse sound is the sound that is present in rooms after reflections from boundary surfaces.
Ee
Elastomer/Metal bond
Constant quality checks at all stages of processing ensure a high and consistent standard for the bond. The final test is a test according to a sampling plan for adhesive strength by visual inspection at the edge zone at 1.5–3 N/mm² tensile force or even by tearing until destruction. In general, it can be said that elastomer/metal bonds, after cross-linking of the elastomer with simultaneous bonding reaction of the adhesive system, show only a break in the elastomer when tested statically.Elastomers
Elastomers are dimensionally stable yet deformable plastics that return to their original shape after being subjected to tensile or compressive stress. Elastomers are also commonly referred to as rubber.EN 45545
The rail vehicle standard DIN EN 45545-2 (CEN TS 45545-2) is a European rail vehicle standard. This standard completely replaces national standards such as DIN 5510. Requirement set R1, which is attached to the standard, is one of the most difficult to fulfill in terms of test methods. Operating classes 1–4, which are attached to the standard, regulate hazard levels HL 1–4.EPDM Ethylene propylene diene rubber
EPDM rubber has good resistance to oxygen, ozone, and temperature. EPDM also has above-average chemical resistance. However, its resistance to mineral oil and grease is rather poor. Thanks to its excellent weather and hot water resistance, EPDM rubber is used for profiles and sealing elements.
Ff
FDA compliance
The FDA (Food and Drug Administration) is an American regulatory agency responsible for monitoring all goods sold in the USA. This also includes all imports into the USA, which is why the FDA's regulations are also important for European manufacturers. These regulations are binding for exporters to the US. The FDA imposes extremely strict requirements in the food sector, where a large number of rubber and plastic products are used and therefore come into contact with food or drinking water. The materials must not release any substances into the food. This means that all plastics that come into contact with food must be FDA-compliant.Flowing and setting a spring element
Creep is the time-dependent increase in the elastic spring travel of a spring under constant load. It is a consequence of the reduction in restoring force. The increase in spring travel, which has already reached half its value after 24 hours of loading, can usually be neglected in practice and does not influence the vibration behavior. The permanent residual deformation, including setting, which depends on the number of load cycles and the amplitude and is comparable to creep, is less than 10% of the elastic spring travel for elastomers with good elastic properties.Foaming process
Depending on the type of foam production, the following processes are distinguished: In physical foaming, the material is foamed by a physical process. In chemical foaming, gases are produced during the manufacture of the plastic, which cause the material to foam. In mechanical foaming, air is stirred into the resin or paste to be foamed; the foam solidifies as the resin cross-links.FPM fluororubber
FPM fluorinated rubbers are also known under the brand name Viton. FPM rubber is flame-resistant and, of all elastomers, has outstanding resistance to high temperatures, ozone, oxygen, and chemicals.Frequency
Frequency refers to the number of sound vibrations per second (hertz, Hz).
Hh
Heavy-duty film
Heavy foils are mainly used for soundproofing metal and plastic components that are exposed to strong vibrations. Applying heavy foils increases the mass of these elements, thereby reducing noise. This is referred to as structure-borne sound insulation. Heavy foils made of bitumen or bitumen-free plastic are also suitable for airborne sound insulation.Hertz
Unit of frequency. 1 Hz = one complete oscillation per second.Hysteresis damping
All elastomer materials have hysteresis damping. The damping depends on the rubber quality, temperature, deformation speed, deformation acceleration, shape, and type of stress.
Ii
Impact sound
Walking on floors generates structure-borne sound, some of which is emitted as airborne sound. Impact sound insulation can reduce this emission.Impedance tube
The impedance tube is used to measure the absorption coefficient of a material when sound waves strike it perpendicularly.Installation noise
Installation noise refers to noise caused by heating and air conditioning units, fans, hydraulic systems, and elevators.Insulation
Insulation is the containment of airborne or structure-borne noise or vibrations.Isolation of structure-borne noise
The known effects of structure-borne noise make it essential to create effective vibration isolation. A relatively simple type of structure-borne noise isolation can be achieved by installing an intermediate layer as close as possible to the source of the disturbance, which interrupts the path of the sound vibrations. For example, motors are placed on specially designed vibration isolation bodies, which form a vibration system that is almost independent of the environment or support. The same applies to building floors, which are periodically subjected to powerful horizontal and vertical impulses at the same time and which are then freed from vibration both horizontally and vertically by means of insulation.
Ll
Listening area
The human ear can perceive sounds in a frequency range from approximately 16 to approximately 16,000 hertz.
Mm
Main excitation frequency
It is essential to correctly identify the dominant excitation frequency in each vibration system. The majority of vibration-exciting systems that require elastic mountings are combinations of drive motors and working machines. In most cases, other vibrations with higher frequencies are superimposed on the fundamental vibration of working machines and aggregates. These arise from the unbalanced movements of masses and cause vibrations that can also occur unevenly or periodically. On the one hand, the excitation frequencies can be determined fairly accurately from the speeds, as is the case with motors. In many other cases, such as textile machines and machine tools, they are almost impossible to determine mathematically, and vibration measurements should be carried out.MVSS 302
Acoustic foams that meet the FMVSS 302 fire safety standard are primarily used in vehicle and machine construction. The addition of flame retardants to the foam limits the rate of flame spread in the event of a fire (4 inches/minute). The test procedure introduced in the USA as Federal Motor Vehicle Safety Standard (FMVSS 302) is used by most automobile manufacturers worldwide.
Nn
Natural or synthetic rubber
As a rough definition of natural rubber and synthetic rubber, it should be noted that natural rubber (NR) is a naturally produced material that serves as a model for all synthetically produced elastomeric materials in terms of its structure. NR has very high tensile strength and, especially in soft elastomer grades, high elasticity, cold flexibility, and excellent dynamic properties, which are rarely achieved in this combination by synthetic elastomers and therefore still make NR indispensable for some applications, especially for vibration isolation systems. Dynamic hardening must also be taken into account when designing elastomer springs. In low-damping elastomer materials such as NR, it can generally be neglected. In highly damping compounds, the dynamic spring stiffness can be several times higher than the static stiffness. However, if a product is subject to extreme demands in terms of certain properties, including oxidation and damping characteristics, it is essential to switch to a synthetic rubber.NBR nitrile rubber
NBR acrylonitrile butadiene rubber (nitrile rubber) impresses with its exceptionally good mineral oil and fuel resistance as well as low compression set. This makes NBR the perfect oil and fuel-resistant sealing material. However, NBR rubber has the disadvantage of very poor ozone resistance.Non-crosslinked foam
Non-crosslinked foam has unbranched molecular chains. This results in lower mechanical and thermal resilience. Non-crosslinked foams are mainly used in logistics packaging.NR Natural rubber
Natural rubber is obtained by tapping rubber trees, which produces a white, watery milk (latex) containing natural rubber. Natural rubber (NR) is an excellent material and has very high tensile strength, elasticity, cold flexibility, and very good dynamic properties. This extraordinary combination is only achieved to a limited extent by synthetic elastomers, which is why natural rubber is still irreplaceable for various applications today. Additional treatment with protective agents is necessary to achieve higher aging and ozone resistance. Furthermore, NR natural rubber is not resistant to mineral oils and greases. NR is available in Shore A hardness ranges of 30–90. Areas of application include molded rubber parts, rubber bellows, rubber membranes, flat rubber seals, etc.NR/SBR Natural/styrene-butadiene rubber
Natural/SBR rubber is particularly valued in environments where it is exposed to heavy wear due to friction or constantly rubbing elements. NR/SBR quality is not resistant to mineral oils and fats.
Pp
Primer
A primer with a 2-component adhesion system is used to improve the adhesion properties. The primer does not contain any crosslinking agents, so the bond to the substrate is created exclusively by physical forces (adhesion).PU polyurethane rubbers
PU polyurethane rubbers are characterized by excellent wear resistance and exceptionally high tear resistance. Their high elasticity and good resistance to high-energy radiation are further positive factors. They are also resistant to oxygen, ozone, mineral oils, and fats. Their hydrolysis resistance is limited when exposed to aqueous media. AU polyurethane rubbers are primarily used as scrapers or for rollers and wheels.
Rr
REACH and foam
Vibraplast AG exclusively processes REACH-compliant foams.Rebound elasticity
Rebound elasticity is the percentage of energy returned and is used to assess elasticity behavior. It indicates the extent to which the material behaves elastically and viscously. The less deformation energy is converted into heat, the greater the elasticity. This test is particularly suitable for providing initial indications of the dynamic behavior of an elastomer using simple means. Rebound elasticity is highly dependent on temperature.Reflection
Reflection is the bouncing back of sound waves.Resonance
Resonance occurs when a vibrating system is excited at its natural frequency.Reticulating
Reticulation is a post-treatment of foams to achieve liquid, air, or gas permeability. This involves removing the cell membranes between the foam webs, while retaining the basic structure of the foam. Only the thin membranes between the foam cells are removed, resulting in an open-cell foam that is permeable to air or liquids.Reverberation
Reverberation is the persistence of sound after the sound source has stopped, heard in rooms and in musical instruments.Reverberation time
Reverberation time is the echoiness of a room. The longer the reverberation time, the longer a sound event can be heard in the room, and the more it echoes and reverberates.Room acoustics
Room acoustics is a subfield of acoustics. This field deals with the distribution of sound levels in rooms. Room acoustics deals with the acoustic environment in interior spaces, which contributes to improving speech or music intelligibility and reducing sound levels.Room sound absorption
Installing sound absorbers on the interior surfaces of a room reduces sound reflection, thereby shortening the reverberation time and improving the room's acoustics.Rubber
Rubber is the uncrosslinked starting product required for the manufacture of elastomers (rubber). A distinction is made between natural and synthetic rubbers.Rubber processing methods
The vulcanization tool or mold required contains one or more cavities, depending on the size, sensitivity, and output capacity of the rubber/metal part. The mold is first loaded with the prepared metal in the open state and then, depending on the process, loaded with the precise volume of mixture in the open or closed mold state. Possible processing methods are compression molding, transfer molding, or injection molding.Rubber-metal compounds
The most commonly used material for rubber-metal compounds is steel, but other metals such as zinc, aluminum, zinc, and alloys can also be used.Rubber-plastic compound
Plastics can also be used instead of metals in rubber-metal compounds. In addition to weight reduction, freedom from corrosion is another advantage. Complex plastic parts can also be efficiently manufactured using injection molding. Similar to metal, the plastics are degreased and mechanically prepared, and then coated with a bonding agent. For the production of rubber-plastic compounds, thermoplastics must be dimensionally stable at vulcanization temperatures of 160–200 °C, otherwise deformation of the plastic part may occur during rubber/plastic molded part production.
Ss
Shear stress
Under shear stress, the linearity limit is 35% deformation, based on the rubber layer thickness. The shear modulus G is the only material constant for elastomers and is determined for each mixture depending on the Shore hardness.Shielding factor
The reduction in the sound level of sound waves through shielding such as noise barriers or partitions is called the shielding coefficient.Shore A hardness
Hardness is commonly expressed using the designation Shore A. This measures the resistance to the penetration of a cone. Finished parts whose test surface deviates from a minimum diameter of 30 mm and a minimum test thickness of 6 mm are only to be regarded as comparative values for values measured under the same conditions and not as material constants.Shore hardness
The most commonly used hardness test for elastomers is the Shore hardness test in accordance with DIN ISO 7619-1. Shore hardness refers to the resistance of a rubber sample to the penetration of a cone-shaped body of specific dimensions under a defined compressive force. Depending on the design of the measuring body, a distinction is made between Shore A for softer elastomer compounds and Shore D for harder elastomer compounds. In order to achieve a flawless measurement of Shore hardness, the standard specifies a sample thickness of 6 mm. If measurements are carried out on finished parts with a lower wall thickness, this usually leads to incorrect results. Commercially available elastomer compounds for technical rubber molded parts have a hardness range of 20–90 Shore A.SI/MVQ silicone rubber
SI/MVQ is a silicone rubber that has very high heat resistance and extreme cold resistance, as well as very good resistance to oxygen, ozone, and UV rays.Side channel attack
Side path transmission is the transmission of sound through adjacent walls, floors, and ceilings.Sound
Sound consists of vibrations ranging from 16 to 16,000 Hz in solids (structure-borne sound) and in the air (airborne sound).Sound absorption
Sound waves never propagate without loss, but are always subject to a greater or lesser degree of attenuation—absorption. Porous materials can achieve a high degree of absorption. Sound absorption is very important for the acoustic experience of a room's users. Appropriate sound absorption allows the room to be tailored to its intended use.Sound absorption coefficient
The sound absorption coefficient α defines the ratio of absorbed to incident sound energy. Complete reflection results in α = 0, while complete absorption results in α = 1. Sound absorption refers to the reduction of sound energy, primarily through conversion into heat. The movement of air molecules (= sound) is converted into heat energy (absorption is synonymous with “swallowing” and “soaking up”). The sound absorption coefficient is frequency-dependent, which is why it is measured in the frequency range from 100 to 5000 Hz.Sound attenuation
Sound absorption can be understood as the prevention of sound propagation through the absorption of airborne sound. During sound absorption, sound energy is converted into inaudible vibration waves, thereby reducing reflection at an interface. This improves the acoustics within the room and reduces noise.Sound attenuation
Sound attenuation can be understood as the prevention of sound propagation through the absorption of airborne sound. During sound absorption, the acoustic energy is converted into non-audible vibrational energy, thereby reducing reflection at boundary surfaces. This improves the acoustics within the room and reduces noise.Sound bridges
Sound bridges are usually undesirable transmission paths for sound and can be largely eliminated with a wide variety of noise reduction measures.Sound insulation
Sound insulation focuses on acoustically separating rooms from unwanted noise from neighboring rooms or from outside. The propagation of airborne or structure-borne noise is prevented by reflection at the transition between two media.Sound insulation composite systems
To achieve optimal results, combined materials can also be used as composite systems for structure-borne sound insulation or airborne sound insulation. For example, multi-layer PUR foams supplemented with a viscoelastic heavy film.Sound insulation index
The sound insulation index R is a logarithmic value that describes the airborne sound insulation performance. The sound insulation index is expressed in decibels.Sound insulation index (R)
Indicates the airborne sound insulation of a building element. R = 10 log (incident sound power / transmitted sound power).Sound propagation
Sound waves propagate spherically at the speed of sound and decrease in intensity with increasing distance. This process is greatly influenced by the absorption of sound waves. A distinction is made between two limiting cases: 1. undisturbed sound propagation in a free field and 2. total sound reflection. The type of sound propagation in a company's workspace will usually fall between these two idealized extreme cases. In room acoustics, the structural and technical design of the environment or the surrounding room is described by parameters such as sound absorption coefficient, sound insulation index, insertion loss, and reverberation time. These parameters are important tools in noise reduction technology.Sound reflection
For all noise problems related to sound insulation or sound absorption, the reflection of a sound source off an obstacle, e.g., walls, windows, ceilings, floors, machines, etc., is an important factor. Reflection depends on the frequency and direction of the sound wave to the obstacle, as well as on the nature and surface structure of the reflecting obstacle. The returning, reflected wave overlaps with the outgoing wave and, depending on the conditions, can result in the sound wave being canceled out or amplified in extreme cases. Basically, it can be said that sound-reflective walls cause strong reflection, while sound-absorbent walls can achieve high sound absorption.Spring characteristic curve
The spring characteristic curve refers to the relationship between the force applied and the resulting change in shape or displacement. The spring properties depend on the modulus of elasticity of the elastomer and the geometric dimensions. Therefore, the binding identification of a bonded rubber spring is not the measured elastomer hardness in Shore A, but the spring characteristic curve. A spring stiffness of ±12% corresponds to approx. ±3 Shore A. For standard parts without special measures, the spring stiffness tolerance is ±20%.Standard quality foam
Standard-quality foam is characterized by its density and compression hardness, which are technical indicators of foam quality. Compression hardness describes how foam responds to a defined force. The higher this value, the harder the foam feels. An important quality feature of foam is its density or volume weight in kilograms per cubic meter (kg/m³). As a rule of thumb, a density of 20–30 kg/m³ is suitable for seat and back cushions and inexpensive mattresses, 30–40 kg/m³ describes standard to high quality for seat and back cushions, mattresses, boat, camping, or garden cushions, and 40–50 kg/m³ stands for high-quality to very high-quality, very good permanently elastic qualities for a wide range of applications.Storage
Elastic mounting using vibration isolation elements on machines prevents structure-borne noise from being transmitted into the building structure. This measure minimizes structure-borne noise transmission at the source.Structure-borne noise
Structure-borne noise is sound that propagates through a solid body. The transmission of sound to a solid body causes it to vibrate. This is how sound propagates through thin-walled sheets or masonry, for example.Structure-borne sound insulation
While the construction materials used in machines and buildings, such as cast iron, steel, and concrete, are good sound conductors and can therefore be described as sound-reflective, rubber, on the other hand, is a poor sound conductor and is therefore very well suited as a sound-absorbing material for structure-borne sound insulation. The insulating effect for structure-borne sound waves is achieved by their partial reflection at the interface of the materials, with only some of them penetrating the intermediate layer.
Tt
Thermal conductivity
The thermal conductivity is decisive for the thermal insulation properties of an insulating material. The thermal insulation property indicates how much heat energy (W) flows through a component per meter (m) at a temperature difference of 1 Kelvin. The unit of measurement is W/mK and is abbreviated as small lambda (λ). The basic rule is: the smaller this value, the better the thermal insulation properties of the insulating material. Examples: PUR foam 0.037 / Vibra®fiber polyester fiber mats 0.037 / Basotect® melamine foam 0.033.Thermoplastic elastomers
Thermoplastic elastomers (TPE) are plastics that can be compared to classic elastomers at room temperature. However, TPE plastics can be plastically deformed when heat is applied.Thermosets
Thermosets are hard polymer materials, some of which are reinforced with glass fiber. Once a thermoset plastic has hardened, it can no longer be reshaped. Thermoset plastics are the right choice when high demands are placed on chemical resistance, heat resistance, chemical resistance, and electrical insulation properties.Types of loading of rubber
When designing bound rubber springs, it is important to note that the degree of deformation varies depending on the type of stress, even when the same force is applied. The designer can choose the direction of the force to subject the rubber to compression, tension, shear, or bending. Shear stresses result in the greatest deformation, while compression stresses result in the least. Tension stresses should be avoided due to the non-linear spring characteristic curve, the tendency to flow, and the poorer force transmission.
Uu
UL 94 fire standard
The UL 94 standard was developed to regulate fire safety testing of plastics, especially foams. This standard was originally used in the USA for testing plastics. However, it has now become established worldwide for classifying the flame resistance and fire safety of plastics and foams.
Vv