Impact sound insulation

Impact sound is the structure-borne sound that is made by footsteps or a similar impact on a ceiling, staircase or landing, for example; it is then partially emitted as airborne sound.


    Ways that impact sound is transmitted

    As shown in Figure 1, the impact sound is not only transmitted directly (1) but also indirectly (2–6)

    • 1 Direct vertical transmission of impact sound
    • 2 – 6 Secondary transmission: horizontal, vertical and/or diagonal

    Nice to know!

    In contrast to airborne sound, impact sound is created by mechanically stimulating the component directly, such as through:

    • Walking on the floor with hard heels
    • Moving chairs
    • Dropping objects
    • Manual work (knocking, drilling, etc.)
    • Coffee machine
    • Blender
    • etc.

    Active principles

    The impact sound is emitted in the receiving room as airborne sound. The impact sound level (L) is an absolute value. Specifically, this means that a lower impact sound level equals better impact sound insulation. (The opposite applies for  airborne sound insulation: the higher the apparent sound reduction index, the better the sound insulation.)

    Technical building installations

    Structure-borne noise is also caused by building technology. Everyone is familiar with the sound of sanitary facilities, ventilation systems, washing machines, and other household technology. Again, the noise that they make can be  counteracted by decoupling the source of structureborne noise in order to reduce the transmission of noise to other  components. In the case of a washing machine, for example, the easiest way to achieve this is to place an elastic underlay below it. For pipes and fittings, the following applies: the heavier the wall to which they are attached, the lower the noise level.



      The main measures for protecting against impact noise

      • Decoupling the systems e.g. with floating screed. Assumes that there are no rigid connections between the screed and  the primary structure of the building.
      • Generally avoiding sound bridges
      • Impact sound insulation mats
      • Carpets and other soft or yielding floor coverings (linoleum, vinyl tiles, etc.)
      • Minimising flanking
      • Airtight joints
      • etc.

      In practice

      Wooden beam ceilings in old buildings usually have poor insulation properties for impact and airborne sound.

      On   renovation projects, it is important to consider the loadbearing capacity of the beams and the maximum possible  construction height. Cement screeds tend to be unsuitable for weight and construction height reasons.

      With dry  constructions weighted down with Idikell, sound insulation can be improved effectively at a low construction height and mass. Further improvements seen from the top of the ceiling are possible by covering the panelling of the bare ceiling with one or two layers of Idikell.

      On the bottom side, a suspended ceiling decoupled with AmpaphonZ 600 and weighted down with  Idikell improves the sound insulation considerably. Cavities should be filled with insulation featuring high flow resistance.

      Floating screed

      23 Airtight layer Ampatex DB 90
      50 Anti-sound coating / heavy foil Idikell M 4001/05
      60 Edge adhesive Ampacoll RA
      73 Chipboard
      80 Impact sound insulation
      81 Cavity insulation
      83 Permanently elastic cemented joint
      84 Lining
      87 Sliding floor
      88 Floating floor covering
      89 Slag
      90 Formwork
      91 Felt underlay

      Nice to know!

      Provide circumferential joints from 7 to 10 mm. Seal the joints with a suitable sealant. Ensure full air impermeability. It is not advisable to use synthetic insulation materials for sound insulation. Mineral wool with a density of at least 50 to 60 kg/m3 is recommended. For ceiling installation, use edge strips (e.g. Ampaphon Z101) where possible. An airless, nonventilated space in the structure is the best place.


      More about this topic

      Airborne sound insulation

      The transmission of sound from room to room.


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      Impact sound insulation

      Propagation of sound through solid constructions.


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      Sound damping

      Sound absorption by or on a material.


      Find out more

      Sound absorption

      Improved indoor acoustics.


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      Product photo: Idikell 4021, heavy foil for noise protection and sound absorption

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