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The attained attenuation is the reduction of an input signal by means of the resistance towards an output signal.

evaluation filter

When a sound level is indicated with an evaluation filter, the type that was used is specified by the unit it can measure e.g. of dB into dB(A). The value in brackets shows that the corresponding filter was applied to the spectrum. In case that no filter was used, the unit dB(lin) is used.


The propagation of noise waves in a gas is due to longitudinal waves – also called dilatation waves. The motion of particles is called propagation direction. The creation of the gas noise is based on the fact, that due to the stimulation of the air an overand under-pressure is created that will lead to particle movement.


Impedance (Z) is also called an acoustic field impedance and describes the resistance in a levelled field of waves. It is calculated by the relation of pressure (p) to the velocity of sounds (v). Also, the field impedance can be computed by the sound velocity (c), under consideration of the temperature (T) and the density (ρ).


We call noise mechanical oscillations in the human hearing range of 16 Hz to 16,000 Hz.

NOISE level

Used in every-day language and refers to the designations of sound capacity and sound capacity levels, which are normally indicated in Decibels.

reverberation time

The reverberation time describes the precise time it takes a noise pressure level to lose 60 dB of the input signal in the room.

sound intensity

The sound intensity level (LI) is the logarithmic ratio of the sound intensity (I) in a sound field with a reference value of IO.

sound power level

The Sound power level (LW) describes the strength of a sound source.

Sound pressure level

The sound pressure level (LP) describes the sound impact (sound immission) at a certain place. It strongly depends on the type of the environment (indoor, outdoor, distance from the sound source).

Sound reduction index

The sound reduction index (R) is an acoustic quantity which describes the difference between sound emission and sound absorption of a component of one or several shells.


A spectrum is the representation of the signal strength as function of frequency and wavelength.

Structure-borne noise

Structure-borne noise is the propagation of waves in solid bodies. In difference to gas noise and the longitudinal waves the type of propagation can also be carried out in form of transversal, expansion and bending waves. The wave types can be classified according to the propagation direction and depending on the oscillation direction.


Transmission of different sound types (e.g. the stimulation of gas sound compared to solid body sound).


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