Müller BBM Group
Bavarian State Ministry
of the Interior

Those who know nothing must

believe anything.


Marie von Ebner-Eschenbach



  • Decibels (dB): dB is a unit that is used to measure the intensity of sound. The logarithmical unit of measurement is suitable for showing the entire human hearing range.  For the sound pressure level in decibels (dB SPL) the lowest level of sound pressure that the human ear can hear serves as the point of reference. The quietest sound that the human ear can hear is normally 0dB SPL (hearing threshold).
  • dB(A):
    The measuring unit of sound is decibels (dB), in the context of which the frequently used addendum of (A) shows that an evaluation of the different tone pitches (frequencies) adapted to the human hearing took place during the measurement.  This enables statements to be made on how loud or quiet it is when leaves rustle (10dB A), during the ticking of a watch (20dB A), when people talk to each other normally (55dB A), an HGV drives by (85dB A) and an ambulance with a siren (120dB A) drives by at a ten meter distance.
  • Emission:
    The emitting of a noise, e.g. from the road or an industrial operation.
  • Emission location:
    The place that a noise occurs, e.g. a road or an industrial area.
  • Immission:
    The impact of a noise e.g. in a residential area.
  • Immission location:
    The location of the impact of a noise, e.g. residential areas, industrial areas.
  • Average sound level:
    the average sound level summarises all the different values measured
    over a certain time frame to one result.
  • Sound absorption DLa:
    Describes the amount of sound waves which are absorbed by the construction.
  • Sound dampening DLr:
    Provides the sum total of reflected and absorbed sound waves (designates the preventing of the dissemination of airborne sound)

  • Sound/Noise:
    Air particles that oscillate (e.g. tyres skidding on the road) create changes in air pressure. Over and above the area where the sound is experienced as being unpleasant, we talk of noise.