Glossary

Sound propagated in the air in the form of sound waves, as opposed to sound transmission through liquids or solid bodies.

Measures the recovery capacity of an elastomer; ratio of the sample body height before and after compression; testing procedure as per EN ISO 1856; test conditions: deformation to 50 % at 23 °C, duration of load 72 h and measurement 30 min after load removal.

The elastomer is subject to a forced sinusoidal vibration. The test parameters are frequency, pre-load and amplitude. Based on the force and deformation result, the dynamic stiffness, the dynamic modulus of elasticity or dynamic bedding modulus and the  mechanical loss factor can be derived. The data sheets usually use the frequencies 10 and 30 Hz with a velocity level of 100 dBv. Testing procedures similar to DIN 53513.

Vibration isolation consisting of an elastic bearing system for an oscillatory system, so that no disturbing vibrations are emitted into the surroundings.

Vibration isolation of a system (recipient) against disturbing vibrations from the surroundings.

Also known as ‘characteristic acoustic impedance’. The greater the difference between the characteristic acoustic impedances of two media, the more sound energy will be reflected at the boundary surface between the two media, i.e. less sound energy is transmitted. Conversely, this also represents better vibration isolation; For good damping there is a so-called ‘jump in impedance’, i.e. a significant difference between the characteristic acoustic impedance of the two media involved.

In respect of vibration isolation this factor characterizes the isolation efficiency as a ratio of input and response forces and/or input and output amplitudes.

Measurement for the efficiency of dampening by a partition element which is located between the concrete sub base and the flooring material; dampening of impact noise is frequency dependent.

Load peaks are maximum loads which occure for short-term and infrequent and can be absorbed by the material without relevant changes of the material properties. Cellular elastomers can absorb load peaks of well over 20 times the static range of use stated in the material data sheets without suffering damage. More compact elastomers can absorb load peaks of 5 to 10 times the static load range.

The mechanical loss factor η is a measure of mechanical damping of viscoelastic materials. With respect to harmonic loads, the mechanical loss factor η can be calculated by the dissipated energy per cycle (hysteresis) related to stored energy during loading by the following formula η = dissipated energy / (2 . π . stored energy). Furthermore the mechanical loss factor η can be derived by measuring the angle of loss δ, when harmonic loads are applied. The tangent of angle of loss δ corresponds to the mechanical loss factor η (η = tan(δ)). Test methods in accordance to DIN 53513; see also damping ratio, angle of loss

Frequency of a system’s free vibration after one excitation; the period of the vibration is dependent on the damping.

Noise emission refers to structureborne noise or  airborne noise emitted by a sound source; the sound source is located at the emission location.

Noise immission is the structureborne noise or airborne noise striking a recipient, regardless of the location of the noise emission (source of the structure-borne or airborne noise). The location of the recipient is referred to as the immission location and the level of sound measured there is known as the immission level.

Describes the relationship between specific load and deflection in graphic form; depending on the load speed; depending on load acceleration, a distinction is drawn between quasistatic and dynamic load deflection curves. In the data sheets the load deflection curve is usually depicted with compression deformation of 40 %, with 20 s rise and decay duration of the load ramp. The elastomer is usually pre-stressed with two preliminary cycles, and measurements are carried out for the third cycle.

When the disturbing frequency of a system is equal to the natural frequency of the system, resonance occurs. Occurrence of resonance can lead to the destruction of the entire oscillating system. By damping the vibratory system it is possible to limit resonance vibrations to an acceptable degree. Flexibility to a changing force is particularly strong with the resonance range.

Smallest pressure and density oscillations in an elastic medium in the audible range of humans from approximately 16 Hz to 20,000 Hz, e.g. airborne sound, structure-borne noise, sound transmitted through liquids. Lower frequencies are referred to as infrasound and higher frequencies as ultrasound.

The maximum compression stress for stationary loads up to which the elastomer will retain its elastic properties; resilient bearings are generally designed for the upper limit of the static range of use in order to achieve maximum vibration isolation.

Are vibrations transmitted via solid or liquid bodies.

Lowest vertical natural frequency of an elastically-mounted system (machine, track superstructure, building, etc.); the lower the tuning frequency, the higher the level of vibration isolation.

In respect of vibration isolation the isolation efficiency as a ratio of input and response forces and/or input and output amplitudes.

Vibrations are processes in which a physical quantity changes periodically depending on time; these physical quantities can be displacements, accelerations, forces, momentum.