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Different types of noise

Airborne noise

Airborne noise is noise that is transmitted from one room to another via the air. Examples of this include noise from the shooting range, jacuzzi, machines, gyms, office landscapes and traffic noise.

Structural noise

Structural noise is noise that is transmitted from one room to another via vibrations in building structures. Examples of structure-borne noise include bass from music, cars, noise from workplaces, engines and generators that go via the contact point into the structure and propagate. This is noise that can be harmful over time. Structural noise and vibration noise can be measured with a vibration meter.

Flank Noise

Transmission of noise around a building element, instead of through the building element itself. Flanking can describe the transmission of noise through holes and cracks, incorrectly sealed transitions between two materials or other indirect paths such as ventilation systems or roof cavities. These noise flanking paths can overcome noise reduction techniques.


Caused by shocks to walls or floors in an adjoining room. Typical sources for this are footsteps on the floor above the home, washers, dryers and cabinet doors mounted on a common wall.

The reverb/echo

Noise made in the same room as you. Hard surfaces throw the sounds back and forth and it can take a long time before the sound dies out. The ability of the individual material to absorb sound varies considerably and is measured in NRC.

The absorbency NRC (Noise Reduction Coefficient) goes on a scale from 0 to 1. If the material has an NRC of 0, it means that it does not absorb noise at all and everything is thrown back. Materials such as ceramic tiles, concrete, etc. is very close to 0. If the number is 1, it absorbs everything that hits. Thick rugs, curtains, etc. helps well, and if you use sound-absorbing boards in acoustic felt or foam, these will be close to 1. NRC on hard surfaces is usually 0.02-0.05. Absorbents in acoustic foam or felt are normally at NRC 0.75 - 0.90.

In a kindergarten, it is normal to want a maximum reverberation time of 0.6 seconds. If you enter the room dimensions x the absorbent factor, you will see that at normal frequencies, with unfortunate combinations of concrete floors and plasterboard, you can quickly get well over 0.6 seconds, preferably up to 2 and more. This is very unfortunate for the work environment, especially over time.

The acoustics of a room can be defined by measuring its reverberation time. The reverberation time (RT) is a measure of the time it takes for an audio signal to fall by 60 dB (RT60). A tiled bathroom with many hard surfaces has a long reverberation time. A carpeted room has a shorter reverberation time. A noise source will generate higher sound pressure levels in a reverberant space because the sound energy takes longer to decay. Noise in a "lively" room can in practice be 5-7 dB louder than in an acoustic "dead" room.

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