Audible range
The human ear can perceive sounds in a frequency range from about 16 to about 16000 Hertz.
Acoustics
The theory of sound and mechanical vibrations is called acoustics.
Absorption
Absorption (damping) comes from the Latin and means to suck in or devour. Absorption is the absorption of sound waves by an absorbing material.
AU Polyurethane rubbers
Polyurethane rubbers are characterized by their excellent wear behavior and exceptionally high level of resistance. High elasticity and good resistance to high-energy radiation are further positive factors, as well as resistance to oxygen, ozone, mineral oils and greases. The hydrolysis resistance is limited in relation to aqueous media. AU polyurethane rubbers are mainly used as wipers or rollers and wheels.
Aging
Ageing is the gradual destruction of elastomers by oxygen, ozone, light, heat, moisture and high-energy radiation, which individually or together can cause progressive irreversible damage
Absorber
Absorbers are materials or constructions that absorb sound.
Porous foams and fibrous materials are often used to absorb airborne sound. Tough plastic heavy foils are applied to solid structures such as thin-walled metal sheets to absorb structure-borne sound.
Airborne sound
Airborne sound is the sound that propagates in the air by means of sound waves.
Architectural acoustics is concerned with the effects of structural conditions on sound spreading between the rooms of a building and, more broadly, between the interior and the outside world. The following areas of building acoustics are covered: structure-borne sound, airborne sound insulation, sound insulation of technical and sanitary facilities.
By-path transmission
By-path transmission is the transmission of sound through adjacent walls, floors and ceilings.
Cross-linked foam
In a cross-linked foam, the molecular chains branch out and are chemically and physically connected by polymerisation. Cross-linking results in an increase in mechanical and thermal resilience.
The cross-linked foams in our range include Plastazote PE foam.
Compression transfer moulding process (CTM)
In the Compression-Transfermolding (CTM) injection molding process, inserted rubber compound is injected through channels into the mold cavities when the press is closed. CTM tools are made in three parts (upper, middle and lower part).
Since the Compression Transfer Moulding (CTM) process generates frictional heat by injecting into the nests, the vulcanization time is reduced.
The transfer moulding process is particularly suitable for the production of small rubber moulded parts in moulds with many nests.
CR Chloroprene rubber
CR chloroprene rubber, is also very common under the trade name Neoprene. CR rubber achieves quite good ozone and ageing resistance but only satisfactory oil resistance. Thanks to the high chlorine content, CR rubber has good flame resistance.
Wherever good flame resistance, good chemical resistance and good aging properties are required, CR chloroprene rubber can be used.
Compression set
The compression set (DVR) is a measure of how elastomers behave during long-term, constant compression deformation and subsequent relaxation.
A DVR of 0% would mean that the rubber has fully regained its original thickness, a DVR of 100% indicates that the rubber was completely deformed during the test and shows no recovery.
Causing vibrations
Moving parts on machines, equipment, apparatus and vehicles generate vibrations and noise. They are caused by uneven or rotating movements of unbalanced masses. Vibrations and shocks act as vibrations and noise disturb the environment.
Compressive stress rubber
Under compressive stress, the limit of linearity is 15% deformation in relation to the rubber layer thickness. Whenever a rubber spring is designed for the compression range, the influence of the form factor must be taken into account. The form factor is the ratio of the action pressure area to the free pressure area of the rubber spring. This is due to the prevented transverse expansion and thus the variable modulus of elasticity c of the incompressible material rubber.
Cellular structure of foam
Depending on the material type or material treatment, the cell structure is open, semi-open or closed.
Closed-cell foams are for example cellular rubber or cross-linked PE foams.
Open-cell foams are normally PUR foams. During subsequent material treatment, such as reticulation, the cell walls are removed through a controlled gas explosion, resulting in open or semi-open cells, e.g. in filter foams.
Cross-linked foam
The cross-linked foam is chemically and physically bonded together by polymerisation, the molecule chains branch out, which leads to an increase in mechanical and thermal resilience.
cold foam
The best and most valuable of all foams is the cold foam, which can be compared to natural latex foam and is mostly used in the block foam process. The cold foam is a polyether foam, which is classified as a highly elastic HR foam (HR= High Resilent) in contrast to the standard foam. The cold foam has the following advantages: open-cell, high air permeability, breathable, irregular, coarse pore structure, high elasticity with a supple handle.
Compression hardness
The compression hardness or also called compression resistance is the pressure required to compress a foam. At a compression hardness of 60, 6.6 kPa (kiloPascal) is required to compress the foam to 40%.
The compression hardness of a foam describes its strength
Cellular rubber and sponge rubber are often confused, the difference is due to the different manufacturing processes in the material properties. Sponge rubber has open cells and a dense outer skin. Due to the outer skin, sponge rubber is particularly suitable for applications involving increased mechanical stress and abrasion. However, if the outer skin is damaged by the foam rubber, it can soak up water. Cellular rubber has no outer skin, but cellular rubber has closed cells. Cellular rubber is therefore always water and airtight. Sponge rubber or cellular rubber are foamed rubber qualities (EPDM, SBR, CR, NBR) and can adapt very well to the substrate, which is why they are mainly used for seals
Diffuse and direct sound
Diffuse sound is the sound that is present in rooms after reflections on boundary surfaces.
Decibel (dB)
Decibel (dB) is the unit of volume.
Difference between structure-borne and airborne sound
In simple terms, the expansion medium is the difference between structure-borne sound and airborne sound. Airborne sound spreads through the air in the form of sound waves. However, structure-borne sound propagates in solid bodies such as steel, concrete, wood, stone, etc. This includes, for example, impact sound or the noise generated by building services installations.
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 added to the standard is one of the most difficult to fulfil with regard to test methods.
Operating Class 1-4 attached to the standard regulates the hazard level HL 1-4.
EPDM Ethylene propylene diene rubber
EPDM rubber has good resistance to oxygen, ozone and temperature. EPDM is also characterized by above-average chemical resistance. However, its resistance to mineral oil and grease is rather poor.
Thanks to its very good resistance to weathering and hot water, EPDM rubber is used as profiles and sealing elements.
Elastomers
Elastomers are dimensionally stable, but deformable plastics which return to their original shape after a tensile or compressive load. Elastomers are generally referred to as rubber.
Elastomer/metal bond
Constant quality checks at all stages of processing ensure a high and consistent standard for the binding. The final inspection
is a test according to a sampling plan of the adhesive strength by visual inspection at the edge zone at a tensile force of 1.5 - 3 N/mm2 or even by tearing to destruction. In general, it can be said that elastomer/metal connections after cross-linking of the elastomer with a simultaneous bonding reaction of the adhesive system, statically tested, only a breakage in the elastomer is detected
FDA conformity
The FDA (Food and Drug Administration), is an American supervisory authority, which is responsible for the control of all goods placed on the market in the USA. This includes all imports into the USA, therefore the regulations of the FDA authority are also important for European manufacturers. These regulations are binding for exporters to the USA. The FDA sets extremely strict requirements in the food sector where a large number of rubber and plastic products are used and as a result come into contact with food or drinking water. The materials must not release any ingredients into the food. As a result, all plastics that come into contact with food should be FDA-compliant.
Foaming process
A distinction is made depending on the type of foam production:
- 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 up.
- In mechanical foaming, air is stirred into the resin or paste to be foamed, through
the cross-linking of the resin, this foam solidifies.
Frequency
The frequency is the number of oscillations of the sound per second (Hertz Hz).
FPM Fluorinated rubber
FPM fluororubbers 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.
Flowing and setting
The flow is the time-dependent increase of the elastic spring travel of a spring under constant load. It is a consequence of the decrease of the restoring force. The increase in spring travel, which has already reached half the value after 24 hours of loading, can usually be neglected in practice and does not influence the vibration behaviour. The permanent deformation residue, including the settling, which depends on the number of load cycles and the amplitude and is comparable with the flow, is less than 10% of the elastic spring deflection for good elastic elastomer qualities.
Heavy foil
Heavy foils are mainly used for anti-drumming of metal and plastic components which are exposed to strong vibrations. By applying heavy foils the mass of these elements is increased and noise reduction is achieved. This is known as structure-borne sound insulation.
Heavy foils made of bitumen or bitumen-free plastic are also suitable for airborne sound insulation.
Hall
Reverberation is the reverberation of what you hear after the end of sound excitation in rooms and musical instruments.
Hardness according to Shore A
Hardness is commonly expressed with the designation Shore A. It is used to measure the resistance against the penetration of a cone. Finished parts whose test surface is at least 30 mm in diameter and whose test thickness is at least 6 mm shall be considered only as reference values for values measured under the same conditions, not as material constants
Hysteresis Damping
All elastomer materials have hysteresis damping. The damping depends on the rubber quality, temperature, deformation speed, deformation acceleration, shaping and type of stress
Hertz
Unit of frequency. 1 Hz = one complete oscillation per second
Installation sound
Installation noise is the noise caused by heating and air-conditioning equipment, fans, hydraulic systems and lifts.
Insulation of the structure-borne sound
The well-known effects of structure-borne noise result in the unavoidable need to create effective vibration insulation. A technologically relatively simple type of structure-borne sound insulation is achieved by installing an intermediate layer as close as possible to the source of interference, which interrupts the path of the sound vibrations. Motors, for example, are placed on specially designed vibration insulation bodies, thereby forming a vibration system 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, which are then freed from vibrations both horizontally and vertically by insulation.
Impendence tube
The impedance tube is used to measure the absorption coefficient of a material at vertical sound incidence.
Impact sound
Walking on floors stimulates structure-borne sound, which is partly radiated as airborne sound. This radiation can be reduced by impact sound insulation.
Isolation
Insulation is the containment of airborne or structure-borne noise or vibrations.
MVSS
Acoustic foams which have the fire protection class FMVSS 302 are mainly used in vehicle and machine construction. By adding flame retardant to the foam, the speed of flame propagation in case of fire is reduced. (4 inch/minute)
The test method introduced in the USA as the Federal Motor Vehicle Safety Standard (FMVSS 302) is used by most of the world's automobile manufacturers.
Main excitation frequency
It is essential that the main excitation frequency dominating in each vibration system is correctly recorded. The majority of vibration excitation systems that require elastic mountings are combinations of drive motors and driven machines. In most cases, the basic vibration of working machines and aggregates is overlaid by other vibrations with higher frequencies, which are caused by the unbalanced movements of masses and which cause vibrations, which can also occur unevenly or periodically. Thereby once the excitation frequencies can be determined quite exactly from the rotational speeds, as in the case of motors. In many other cases, as with textile machines and machine tools, they are almost impossible to determine mathematically and vibration measurements should be carried out.
Non cross-linked foam
An uncrosslinked foam has unbranched molecule chains. This results in a lower mechanical and thermal resilience.
The main area of application for non-crosslinked foams is logistics packaging.
NR/SBR Natural/styrene butadiene rubber
Natural/SBR rubber is particularly valued in environments where they are subject to heavy wear from friction or in constantly abrasive elements. The NR/SBR quality has no resistance to mineral oils and greases.
NBR Nitrile rubber
NBR Acrylonitrile-Butadiene rubber (Nitrile Rubber) is characterized by its exceptionally good resistance to mineral oil and fuel, as well as a low compression set. Therefore NBR is the perfect oil and fuel resistant sealing material. The very poor ozone resistance of NBR rubber has a negative effect.
Natural or synthetic rubber
For a rough definition of natural rubber or synthetic rubber, natural rubber (NR) is a material produced by nature, all synthetically produced elastomeric materials, is a model in terms of its structure. NR has a very high tensile strength, especially in soft elastomer qualities, a high elasticity, flexibility at low temperatures and excellent dynamic properties, which are hardly ever achieved by synthetic elastomers in this combination and therefore make NR indispensable for some applications, especially for vibration insulation systems, even today.
When designing elastomer springs, dynamic hardening must also be taken into account. With low-damping elastomer materials such as NR, it can generally be neglected. With highly damping compounds, the dynamic spring stiffness can be several times higher than the static one.
If, however, extreme demands are made on a product with regard to certain resistances, including oxidation and damping properties, it is essential to switch to synthetic rubber.
Natural rubber
Natural rubber is obtained by tapping rubber trees and harvesting a white aqueous milk (latex), the natural rubber. Natural rubber (NR) is an excellent material and has a very high tensile strength, elasticity, low-temperature flexibility and very good dynamic properties. This extraordinary combination is only achieved to a limited extent by synthetic elastomers and therefore natural rubber is still irreplaceable for various applications. An additional finish with protective agents for a higher resistance to ageing and ozone is necessary. Furthermore, NR natural rubber is not resistant to mineral oils and greases.
NR is available for Shore A 30-90 hardness ranges.
Fields of application: moulded rubber parts, rubber bellows, rubber membranes, rubber flat seals ecc
Noise insulation composite systems
For an optimal result, combined materials can also be applied as composite systems for damping structure-borne or airborne sound. For example, multi-layer PUR foams can be supplemented with a viscoelastic heavy foil.
Primer
To improve the adhesion properties, a primer with a 2-component adhesive system is used. The primer does not contain any crosslinker, so the bond to the substrate is created exclusively by physical forces. (Adhesion)
REACH and foam
Vibraplast AG processes only REACH compliant foams.
Reticulate
Reticulation is a post-treatment of foams to achieve liquid, air or gas permeability.
In this process, the cell membranes between the foam webs are removed, but the basic structure of the foam remains intact. Only the thin intermediate skins of the foam are removed, thereby creating an open-cell foam that is permeable to air or liquid.
Response
One speaks of resonance when an oscillating system is excited with its natural frequency.
Reflection
Reflection is the reflection of sound waves.
Room acoustics
A sub-area of acoustics is room acoustics, this area deals with the sound level distribution in rooms. Room acoustics deals with the acoustic room climate in interiors, which contributes to the improvement of speech or music intelligibility and the reduction of the sound level.
Reverberation time
Reverberation time is the reverberation of a room. The longer the reverberation time, the longer a sound event can be heard in the room, the more it sounds and reverberates.
Rubber processing methods
The required vulcanizing tool or mold contains one or more nests depending on the size, sensitivity and output of the rubber/metal part.
The mould is first charged with the prepared metal in the open state and then, depending on the process, with a volume-precise mixture in the open or closed state of the mould. Possible processing methods are compression moulding, transfer moulding or injection moulding.
Rebound Elasticity
Rebound elasticity is the energy returned in percent and is used to assess the elasticity behaviour, which indicates to what extent the material behaves elastically and how viscous. The less deformation energy is converted into heat, the greater the elasticity. This experiment is particularly suitable for providing initial indications of the dynamic behavior of an elastomer by simple means. The rebound elasticity is strongly dependent on temperature
Rubber-to-metal bondings
The most commonly used material for rubber-to-metal bondings is steel, but other metals such as zinc, aluminium, zinc and alloys can also be used.
Rubber
Rubber is the uncrosslinked starting product which is required in the production of elastomers (rubber). A distinction is made between natural and synthetic rubbers.
Room sound absorption
By mounting sound absorbers on the inner surfaces of a room, the sound reflection is reduced, therefore the reverberation time is shortened and the acoustics of the room are improved.
Rubber-plastic compound
Instead of metals in rubber-metal compounds, synthetic materials can also be used. In addition to weight reduction, the absence of corrosion is a further advantage. Even complex plastic parts can be produced efficiently by injection moulding.
Similar to metal, the plastics are degreased and mechanically prepared and coated with an adhesion promoter. 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 can occur during rubber/plastic molding production.
Sound attenuation can be understood as the prevention of sound propagation through the absorption of airborne sound. The sound energy is converted into inaudible oscillation waves during sound absorption and thus the reflection at a boundary surface is reduced accordingly. The acoustics within the room are improved and the noise is reduced.
Sound insulation dimension R'
Indicates the airborne sound insulation of a building element, taking into account the usual building by-passes.
Sound insulation dimension R
Indicates the airborne sound insulation of a building element without taking into account the usual building by-passes.
Sound reduction index (R)
Indicates the airborne sound insulation of a building element. R = 10 log (incident sound power / passing sound power).
Storage
Elastic mounting by vibration insulation elements on machines prevents structure-borne noise from being introduced into the building structure. This measure minimizes the introduction of structure-borne noise at the source.
Cut-off measurement
Reduction of the sound level of sound rays by means of shielding such as noise barriers or movable walls is called shielding dimension.
SI/MVQ silicone rubber
SI/MVQ is a silicone rubber which has a very high heat resistance and extreme cold resistance as well as a very good resistance against oxygen, ozone, UV-rays.
Structure-borne sound insulation
While the construction materials of machines and buildings such as cast iron, steel and concrete are good conductors of sound and are therefore described as sound-reflecting in analogy to the material consistency, rubber, on the other hand, conducts sound poorly and is very well suited as a softer material for structure-borne sound insulation. The damping effect for structure-borne sound waves is due to their partial reflection at the interface of the materials and only a part of them penetrates the intermediate layer.
Shear load
Under shear stress, the linearity limit is 35% deformation, relative to the rubber layer thickness.
The shear modulus G represents the only material constant of elastomers and is fixed for each compound depending on the Shore hardness.
Stress types rubber
When designing bonded rubber springs, it should always be noted that for the same force application, the degree of deformation varies according to the type of stress. By selecting the direction of the force, the designer can have the rubber stressed in compression, tension, shear or bending. Shear stresses result in the greatest deformations, compression stresses in the smallest.
Tensile stresses are to be avoided due to the non-linear spring characteristic curve, due to the flow tendency and due to poorer application of force.
Spring characteristic curve
The spring characteristic curve is the relationship between the applied force and the deformation or displacement resulting from its action.
The spring properties depend on the elastic modulus 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% means approximately ? 3 Shore A. For standard parts without special measures, the spring stiffness tolerance is ? 20%.
Shore hardness
The most commonly used hardness test for elastomers is the Shore hardness test according to DIN ISO 7619-1, which is the resistance of a rubber sample to the penetration of a conical body of a certain size 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 an impeccable measurement of Shore hardness, the standard specifies a sample thickness of 6 mm. If measurements are carried out on finished parts with lower wall thicknesses, these usually lead to incorrect results.
The commercially available elastomer compounds for technical rubber mouldings have a hardness range of 20-90 Shore A.
Sound absorption
Sound waves never propagate without loss, but are always subject to a more or less large damping - absorption. A high degree of absorption can be achieved through porous materials.
Sound absorption is of great importance for the acoustic experience of the users of a room. Through appropriate sound absorption, the room can be adapted to the respective purpose of use.
Sound propagation
Sound waves propagate spherically at the speed of sound and reduce their sound intensity with increasing distance. This process is strongly influenced by absorption of the sound waves. A distinction is made between two limiting cases:
1. undisturbed sound propagation in free field
2. total sound reflection.
The type of sound propagation in the working area of a company will usually be between these two idealized extreme cases. In room acoustics, the structural and technical design of the surroundings or the surrounding room is described by parameters such as sound absorption coefficient, sound insulation level, insertion loss and reverberation time. These parameters are important aids in noise reduction technology.
Sound reflection
For all noise problems related to sound insulation or sound attenuation, the reflection of a sound source from an obstacle, e.g. wall, window, ceiling, floor, machines, etc., must be considered. is an important factor. The reflection depends on the frequency and direction of the sound wave towards the obstacle as well as on the nature and surface structure of the reflecting obstacle.
The returning, reflected wave is superimposed on the incoming wave and, depending on the conditions, in extreme cases results in the sound wave being cancelled or amplified. Basically, it can be said that a strong reflection takes place with sound-hard walls and a high sound absorption can be achieved with sound-soft walls.
Sound
Sound are vibrations from 16 to 16,000 Hz in solids (structure-borne sound) and in the air (airborne sound).
Sound bridges
Sound bridges are the most unwanted transmission paths of sound and can be eliminated to a large extent with various noise reduction measures.
Sound insulation dimension
The sound reduction index R is a logarithmic quantity that describes the airborne sound insulation performance. The sound reduction index is given in decibels.
Standard quality foam
The density and compression hardness describe the technical quality of a foam.
The compression hardness describes the compressive behaviour of foams at a defined force.
The higher this value, the harder the foam feels.
An important quality feature of a foam is its density or volume weight (m3 kilograms per cubic meter).
As a rule of thumb:
-20 - 30 kg/m3 => quality for seat and backrest cushions, low-priced mattresses,
-30 - 40 kg/cbm => standard to high quality for seat and backrest cushions, mattresses, boats, camping or garden cushions etc.,
-40 - 50 kg/cbm => high to very high and very good permanently elastic quality for a wide range of all applications.
Structure-borne sound
Structure-borne noise is sound that propagates in a solid body. Sound transmission to a solid body causes it to vibrate. For example, the sound propagates through thin-walled metal sheets or through the brickwork.
Sound insulation
The acoustic separation of rooms, against unwanted sound from neighbouring rooms or from outside, is the most important aspect of sound insulation. The propagation of airborne or structure-borne sound is prevented by reflection at the transition between two media.
Thermosets
Duroplastics are hard and partially glass fibre reinforced polymer materials. Once a thermoset plastic has cured, it cannot be reshaped. If high demands are placed on chemical resistance, heat resistance, chemical resistance and electrical insulation properties, thermoset plastic is the right material.
Thermal conductivity
The thermal conductivity is decisive for the thermal insulation properties of an insulation material. The thermal insulation property indicates which thermal 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 (?). The basic rule is that the smaller this value, the better the thermal insulation property of the insulating material.
Examples: PUR foam 0.037 / polyester fibre mats Vibra?fibre 0.037 / melamine foam Basotect? 0.033
Thermoplastic Elastomer
Thermoplastic elastomers (TPE) are plastics that can be compared to classical elastomers at room temperature. TPE plastics can, however, be plastically reshaped under heat.
UL 94 Fire standard
The UL 94 regulation was developed for the fire safety testing of plastics, especially foams.
This standard was originally used in the USA for testing plastics. In the meantime, however, it has become accepted worldwide for the classification of the flame resistance and fire safety of plastics/foams.
Vibrations
Vibrations are movements of masses or mass particles around a rest position.
Vibration Technology
The basic principle of vibration isolation is to separate the interfering object (active isolation) or the object to be protected (passive isolation) from each other and to expand isolation materials or rubber satellite elements or springs into a system capable of vibration by means of an intermediate layer. The principle of vibration suppression consists in the fact that by frequency tuning from the excitation frequency to the natural frequency, the movements are no longer synchronous with the interference, but are in opposite phase to it
Viscose Attenuation
Visco-elastic properties under forced vibrations are of importance for elastomers under periodically dynamic stress. Plotted in a stress-deformation diagram, one obtains the shape of an ellipse. The area of the ellipse shows the damping, i.e. the amount of mechanical energy that is converted into heat during each deformation cycle in the elastomer. The amount of heat that cannot be dissipated to the outside heats up the rubber part. Critical values can be achieved at high load change frequencies and large amplitudes.
Vulcanizing
During vulcanisation, the rubber molecule chains are linked together at different locations by a chemical process, thereby preventing the molecule chains from sliding past each other when force is applied, but returning almost completely to their original position once the force has elapsed.
This springback capability or elasticity is what makes rubber so special. No other material shows such elasticity. For this reason, rubber materials are called elastomers
Volume weight
The density is the weight of the foam in kg/m? (kilogram per cubic meter).
The weight or density of the foam is also an indicator of quality, the higher the density, the longer the quality. However, the density has nothing to do with the perceived degree of hardness. As a rule, lighter foams are cheaper because less material is needed.
